I love IE7, but it is by no means the perfect browser.  Along with every other browser out there it can be heavily customised.  Here are the ones I use myself.  There are loads at http://www.windowsmarketplace.com/category.aspx?bcatid=834&tabid=1

ieSpell 
(this is also the spell checker used on the blog site when you are adding something - perhaps into the forums)
IESpell is a free Internet Explorer browser extension that spell-checks text-input boxes on a Web page. It should come in particularly handy for users who do a lot of Web-based text entry (Web mail, forums, blogs, diaries). Even if your Web application already includes spell-checking functionality, this utility is faster than a server-side solution. Plus, you get to store and use your personal word list across all your applications instead of having to maintain separate ones on each application. Version 2.5.1 build 106 may include unspecified updates, enhancements, or bug fixes.

InlineSearch
Inline Search v 1.4.3 (cf. ChangeLog) is an extremely useful free add-on for Internet Explorer that mimics Firefox's search behavior. It turns searching in a web page into a non modal research experience coupled with a find as you type facility. It integrates flawlessly into IE (version 5.5 or above), giving it that little extra that makes you a lot more efficient when you are looking for a specific piece of information.

IE7pro
IE7pro is an must have add-on for Internet Explorer 7, which adds lots of features and extras that make your IE easier, more useful, more secure and more customizable. Some features: Support Double click to close tab; Support mouse gesture; Support view page info and save flash/video; Support session crash recovery; Support block ADs; Support refresh Tab; Support save whole page to image; Support quick switch proxy; Support custom User Agent.Version 0.9.10 adds Web Pages Autoscroll, Enhances tabs management Emulate "Open in New Tab" in context menu when Drag & Drop url; Supports new Tab from search bar; Supports new Tab when left-click in the favorite list.

Star Downloader Free
Star Downloader is a download manager that accelerates your downloads by splitting the files into several parts and downloading them simultaneously. Download speeds are increased further by choosing the fastest mirror sites. Version 1.45 has Firefox 1.5 support and Internet Explorer Toolbar for fast searching.

IE7 Open Last Closed Tab     (functionality is also part of IE7pro)
IE7 Open Last Closed Tab is a plug-in for Internet Explorer 7 that makes "Alt-X" reopen the last closed tab. This is very useful when you accidentally close a tab that you didn't mean to close. Instead of trying to find it in your browser history, you hit "Alt-X" and it automatically reopens in a new tab.

AutoRefresher for IE       (functionality is also part of IE7pro)
This Internet Explorer addon automatically refreshes websites for you. You can set it to refresh your pages at custom intervals or any predefined ones. Each browser window has its own refresh control. Istaller/uninstaller are included with this package. Great for surfing Web pages that are updated often.

Microsoft Fiddler
Fiddler is a HTTP Debugging Proxy, which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP Traffic, set breakpoints, and fiddle with incoming or outgoing data. Fiddler is designed to be much simpler than using NetMon or Achilles, and includes a simple but powerful JScript.NET event-based scripting subsystem. Version 1.1.9 may include unspecified updates, enhancements, or bug fixes.

Favorites Finder
How fast can you get to your favorite Web sites? Is your bookmarks list a mess? The Web sites you visit most often are a few keystrokes away using Favorites Finder. Add as many favorites as you like now; you'll be able to find them by typing a few letters from the website title, address, or folder name. No more scrolling through a long list with your mouse. Once you've filtered your favorites list hit Enter to navigate to the matching site or select from among a few matching sites. It's especially useful for those sites you're always visiting, be it an eBay listing, your webmail, or favorite blog. Favorites Finder runs right inside your Internet Explorer browser.Version 1.1.1 may include unspecified updates, enhancements, or bug fixes.