Mozilla or Firebird. Firebird is based on Mozilla, has a few extra goodies and the menus at the top are organized in a way more familiar to IE users.

Mozilla is faster than IE. It's more standards compliant than IE. TIME magazine voted it the best web browser.

www.mozilla.org
www.mozillazine.org

If you want some addons for Mozilla/Firebird, check out www.mozdev.org - Mycroft and Optimoz are particularly handy.