Web Parts in common with WSSv3
Content Editor Web Part Use for formatted text, tables, and images.
Form Web Part Use to connect simple form controls to other Web Parts.
Image Web Part Use to display pictures and photos.
Members Use the Members Web Part to see a list of the site members and their online status.
Page Viewer Web Part Use to display linked content, such as files, folders, or Web pages. The linked content is isolated from other content on the Web Part Page.
Relevant Documents Use this webpart to display documents that are relevant to the current user.
User Tasks Use this webpart to display tasks that are assigned to the current user.
XML Web Part Use for XML, and XSL Transformation of the XML.
List View Web Part A list view web part is provided for every list created in a site (a list template may include more than one view). The list view renderes the CAML markup defined in the view.
Data View Web Part This web part is configured with SharePoint Designer. It can use a wide range of data sources including XML files, web services, SQL and Oracle databases and SharePoint list/library content. The rendering is XSLT driven with SharePoint Designer providing a drag-and-drop interface to generate the XSL.
Web Parts specific to MOSS 2007
Business Data (Enterprise CAL)
Business Data Actions Display a list of actions from the Business Data Catalog.
Business Data Item Display one item from a data source in the Business Data Catalog.
Business Data Item Builder Creates a Business Data item from parameters in the query string and provides it to other web parts. This web part is only used on Business Data profile pages.
Business Data List Display a list of items from a data source in the Business Data Catalog.
Business Data Related List Display a list of items related to one or more parent items from a data source in the Business Data Catalog.
Content Rollup (Standard CAL)
Colleague Tracker Displays your list of colleagues and any recent changes they made have had.
Memberships Displays your site and distribution list memberships.
My Links Use to display your links
My SharePoint Sites Use to display documents authored by you on sites where you are a member and sites of your choice.
My Workspaces Displays sites created under your My Site.
Site Aggregator Use to display sites of your choice.
Table of Contents You use the Table of Contents Web Part to automatically generate a site map that point to various parts of your Office SharePoint Server 2007 site collection. You can specify which part of your site collection the Web Part should generate links to, how the links are presented, and how the links are organized.
Dashboard (Enterprise CAL)
Key Performance Indicators Shows a list of status indicators. Status indicators display important measures for your organization, and show how your organization is performing with respect to your goals.
KPI Details Displays the details of a single status indicator. Status indicators display an important measure for an organization and may be obtained from other data sources including SharePoint lists, Excel workbooks, and SQL Server 2005 Analysis Services KPIs.
Other
Excel Web Access Use the Excel Web Access to interact with an Excel 2007 workbook as a Web page. (Enterprise Feature)
I need to… Displays tasks and tools from a list
IView Web Part Displays iViews from SAP portal servers. (Enterprise Feature)
RSS Viewer Renders RSS Feed
This Week in Pictures Use to display the images library in the News web
WSRP Consumer Web Part Displays portlets from web sites using WSRP 1.1. (Enterprise Feature)
Filters
Authored List Filter Filter the contents of web parts using a list of values entered by the page author.
Business Data Catalog Filter Filter the contents of web parts using a list of values from the Business Data Catalog.
Current User Filter Filter the contents of web parts by using properties of the current page.
Date Filter Filter the contents of web parts by allowing users to enter or pick a date.
Filter Actions Filter Actions
Page Field Filter Filter the contents of web parts using information about the current page.
Query String (URL) Filter Filter the contents of web parts using values passed via the query string.
SharePoint List Filter Filter the contents of web parts by using a list of values from a Office SharePoint Server list.
SQL Server 2005 Analysis Services Filter Filter the contents of web parts using a list of values from SQL Server 2005 Analysis Services cubes.
Text Filter Filter the contents of web parts by allowing users to enter a text value.
Misc
Contact Details Use to display details about a contact for this page or site
Outlook Web Access
My Calendar Use to display your calendar. This part works with Microsoft Exchange Server 2003 and above.
My Contacts Displays your contacts using Outlook Web Access for Microsoft Exchange Server 2007.
My Inbox Displays your inbox using Outlook Web Access for Microsoft Exchange Server 2003 or later.
My Mail Folder Displays your calendar using Outlook Web Access for Microsoft Exchange Server 2000 or later.
My Tasks Displays your tasks using Outlook Web Access  for Microsoft Exchange Server 2003 or later.
Search
Advanced Search Box Entry point for advanced search
People Search Box Entry point for people search
People Search Core Results Web part to display the people search results.
Search Box Entry point for search.
Search Core Results Web part to display the search results.
Search High Confidence Results Web part to display the special term and high confidence results.
Search Paging Displays search paging.
Search Statistics Displays search statistics.
Search Summary

Displays search summary.

Site Directory
Categories Displays categories from the Site Directory
Sites in Category Displays sites in the Site Directory
Top Sites

Display the top sites from Site Directory

Publishing
Content Query Displays items from any site in current site collection based on site, list, column criteria