Today I've had several calls and IMs from friends who needed help with different tasks: here's a list of programs that I recommended to them as needed.
UNetbootin can make USB keys for different builds of Linux, as well as FreeDOS, some anti-virus tools, and a password cracker if you need it.
VirtualDub lets you slice and convert videos into pieces and different formats.
CCleaner cleans out old Windows files and registry data. It also has a nice startup editor: anything that looks like a nonsense word in that list is probably a virus you can turn off.
Avast is what I use at home and work for anti-virus needs. The free home version is renewable annually, and the corporate version has a nice management system for multiple clients.
Peazip works with ZIP, RAR, 7Z, and a few exotic compression formats as well. Works on Linux and Windows too.
Paint.NET is good for Windows users that need to resize or crop photos, as well as touch them up. If you're on a Linux box, GIMP's probably installed and that works very well.