While preparing an article about general privacy issues, I tested the newest Mozilla Firebird version and came to the conclusion that this will be my new browser recommendation. Very easy to set up, fast and comfortable, it can replace IE with just a few clicks.
Using Mozilla or Firebird has the advantage that both don't support the ActiveX & BHO technology (though there are tries to implement it), which is very often used by hijackers and other malware. And you'll find the integrated popup and spam filters very helpful as well. And if you don't like it, you can always just continue to use IE.
Mozilla (browser, email client and website composer) and Firebird (browser only) are available at www.mozilla.org.

Another recommendation for German users only (sorr, it's available in German only) is PostMe, a easy and secure mail client with a lot of smart functions.