As a computer scientist I use a lot of software, and so here are some of my personal favorites.

(See Disclaimer)

Development

• LINQPad – Easily test LINQ statements, .NET snippets, and .NET assemblies.
• UltraEdit – Robust Text Editor
• WampServer – Windows Installer for Apache, myPHPAdmin, PHP
• Balsamiq Mockup – Create Software Mockups in minutes
• Snagit – Comprehensive Screen Capture Software, with auto-cropping and shadow/border/outline effects

Computer Maintenance

• CCleaner – Clean up junk files on your computer; remove unused registry keys.
• Defraggler – What Windows 7′s defragmenter should be.

Security

• PasswordSafe – Store all your passwords in an encrypted database.
• Microsoft Security Essentials – Anti-Virus protection. Free daily updates to virus definitions.

Internet

• Google Chrome
• Firefox – Simple, really.
  • Adblock Plus – Removes all ads. Be sure to subscribe to an ad list.
  • Update Bookmark – A must have, easily updates bookmarks without going into their properties
  • Tab Mix Plus – Do more with Firefox Tabs.

Misc.

• ComicRack – For reading archived comics.
• GIMP – Open Source Photoshop.
• Paint.NET – Another Paint application.