You can customize each of the standard tabs and types of records, including adding custom fields and setting page layouts. You can also customize search, tagging, and user interface options for your organization.  To tailor for your organization, you can customize the display of the various tabs and other items.  Click Your Name | Setup | Customize and then select a link to view the following customization options:

• Tab Names and Labels - Rename the labels for standard Salesforce tabs and fields.
• Home - Add a logo, dashboard, or links to the Home tab and create additional home page layouts for different users.
• Activities - Customize various options for tasks and events such as fields, page layouts, record types, validation rules, search layouts, and buttons. Also, enable or disable functionality like activity reminder popups and recurring events.
• Campaigns - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations. You can also configure Campaign Influence.
• Campaign Member - (Located under Campaigns) Edit fields, create validation rules and triggers, control the layout, and create custom buttons and links.
• Leads - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations. You can also set up lead queues, assignment rules, lead settings, and online lead capture.
• Accounts - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and for Enterprise, Unlimited, and Developer Edition organizations, create record types and set up account teams.
• Person Accounts - (Located under Accounts) Control the layout of fields, related lists, and custom links, and manage record types.
• Contacts - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations.
• Opportunities - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and for Enterprise, Unlimited, and Developer Edition organizations, create record types and set up team selling.
• Opportunity Products - (Located under Opportunities) Customize the standard fields, create custom fields, and control the layout of fields on product pages within the Opportunities tab.
• Quotes - Customize the standard picklists, create custom fields and custom links, and control the layout of fields, related lists, and custom links, and create PDF templates and terms and conditions.
• Quote Line Items - (Located under Quotes) Customize the standard fields, create custom fields, and control the layout of fields on quote line item pages.
• Forecasts - Customize your fiscal year settings, forecast period, default view, and forecast hierarchy. These options are only available if your organization has enabled customizable forecasting.
• Cases - Customize the standard picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations. You can also set up case queues, case contact roles, assignment, auto-response, and escalation rules, and support settings.
• Case Team - (Located under Cases) Define case teams and case team roles for your organization.
• Email Messages - (Located under Cases) Create triggers for Email-to-Case or On-Demand Email-to-Case messages.
• Case Comments - (Located under Cases) Create triggers for case comments.
• Case Milestones - (Located under Cases) Create validation rules for case milestones.
• Entitlement Management - Set up entitlement management so that support reps can verify if customers are eligible for support and provide the correct service levels to your customers.
• Entitlements - (Located under Entitlement Management) Customize the standard fields, create custom fields and custom links, control the layout of fields, related lists, custom links, and create record types and templates.
• Entitlement Contacts - (Located under Entitlements) Customize the standard fields.
• Service Contracts - (Located under Entitlement Management) Customize the standard fields, create custom fields and custom links, control the layout of fields, related lists, custom links, and create record types.
• Contract Line Items - (Located under Service Contracts) Customize the standard fields, create custom fields and custom links, control the layout of fields, related lists, custom links, and create record types.
• Self-Service - Set up your public solutions, online case capture, and the Self-Service portal.  Note:  Starting with Spring ’12, the Self-Service portal isn’t available for new organizations. Existing organizations continue to have access to the Self-Service portal.
• Call Center - Configure the Salesforce CRM Call Center by defining call centers, adding directory numbers, and customizing SoftPhone layouts.
• Service Cloud Console - Customize, extend, or integrate the footer, sidebars, highlights panels, and interaction logs of the Service Cloud console using Visualforce.
• Contracts - Customize the standard picklist, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations. You can also set the contract expiration notices for your organization and configure auto-calculation of contract end dates.
• Solutions - You can customize the standard solution picklists, create custom fields and custom links, control the layout of fields, related lists, and custom links, and create record types for Enterprise, Unlimited, and Developer Edition organizations.
• Products - For Enterprise, Unlimited, and Developer Edition organizations, set up price books, products, and schedules.
• Partners - Configure your partner portal.
• Salesforce to Salesforce - Enable Salesforce to Salesforce business collaboration both within and across Salesforce organizations.
• Connection Finder - (located under Salesforce to Salesforce) Enable the ability to email partners a survey asking if they use Salesforce. Also, customize default template used for the email and logo used for the survey.
• Customer Portal - Enable the Customer Portal for your organization.
• Chatter Answers - Enable Chatter Answers and configure a Force.com site and Customer Portal to host Web communities for your customers.
• Ideas - Customize the standard picklists, create custom fields, and control the layout of fields for Enterprise, Unlimited, and Developer Edition organizations. You can also establish comment validation rules and manage your communities.
• Assets - Customize the standard fields, create custom fields, control the layout of fields on asset pages, set search results layouts, and create custom links.
• Territories - For Enterprise, Unlimited, and Developer Edition organizations, create and edit custom territory fields.
• Users - Create custom fields and custom links for users.
• Console - Create console layouts that display pertinent information to users.
• Tags - Enable personal and public tags for your organization. You can also delete personal tags.
• Reports & Dashboards - Customize user interface and email settings for reports and dashboards.
• Search - Optimize search settings for your organization.
• Social Accounts and Contacts - Enable and configure Social Accounts and Contacts for your organization.
• User Interface - Enable Quick Create, collapsible page sections, related list hover links, and customize the sidebar for your organization, among other options.