Archiving/compression

The native .zip file integration in Windows Explorer is OK, but most people want something with more features than that. For a long time now, my favorite third-party archiving tool has been Rarlab's shareware WinRAR.

Its proprietary .rar archive format does a far better job of compressing than vanilla .zip does, and includes compression algorithms for audio and images -- ones that aren't already compressed, that is. (Note that while the .rar format is great for your own use and is becoming increasingly widespread, you can't yet assume other users will have a program that understands .rar files.) The trial is free (albeit with nag boxes when the 40-day trial period expires), and a single-user license will cost you $29.

A new contender that's completely free and open source is Igor Pavlov's 7-Zip, which includes your choice of multiple compression algorithms, AES-256 encryption for archives, multithreaded performance for multicore systems and compatibility with existing .rar archives. If you're a convert from WinRAR, you don't have to recompress all your old files. The interface is also similar enough to WinRAR that you can switch from one to the other without too much trouble.