The following is a comprehensive list of all SharePoint 2010 out-of-box web parts, with a couple of screen shots thrown in there!  The groups are just the built-in groupings in the UI

Lists & Libraries

- These are list view web parts for the lists & libraries on the site

Authoring
- Content Editor – Foundation
- Image Viewer – Foundation
- Media Web Part
- Page Viewer – Foundation
- Silverlight Web Part – Foundation

Business Data
- Business Data Actions
- Business Data Catalog Filter
- Business Data Item
- Business Data Item Builder
- Business Data List
- Business Data Related List
- Key Performance Indicators
- KPI Details
- Visio Graphics Service

Content Rollup
- Chart Viewer
- Content Query
- HTML Form Web Part – Foundation
- iView
- Picture Library Slideshow Web Part – Foundation



- RSS Viewer
- What’s Popular – pick from content, search queries, or search results



- XML Viewer – Foundation

Documents
- Document ID Lookup
- Document Set Contents
- Document Set Properties
- Relevant Documents – Foundation

Filters
- Choice Filter
- Current User Filter
- Date Filter
- Filter Actions
- Page Field Filter
- Query String (URL) Filter
- SharePoint List Filter
- SQL Server Analysis Services Filter
- Text Filter


My Information
- My Calendar
- My Contacts
- My Inbox
- My Mail Folder
- My Tasks

Navigation
- Categories
- Site Aggregator
- Sites in Category
- Summary Links
- Table of Contents
- Tag Cloud



Office Client Applications
- Excel Web Access
- InfoPath Form Web Part



- WSRP Viewer

People
- Contact Details
- Profile Browser
- Site Users – Foundation
- User Tasks – Foundation

PerformancePoint
- PerformancePoint Filter
- PerformancePoint Report
- PerformancePoint Scorecard
- PerformancePoint Stack Selector

Search
- Advanced Search Box
- Dual Chinese Search
- Featured Content
- Federated Results
- People Refinement Panel
- People Search Box
- People Search Core Results
- Refinement Panel
- Related Queries
- Search Action Links
- Search Best Bets
- Search Box
- Search Core Results
- Search Paging
- Search Statistics
- Search Summary
- Top Federated Results

Miscellaneous
 - Chart Web Part