Here is a quick list of some software that you are probably not using, but should be.

1) Colorpic: I have been using this for over a year now.  It is a free program that allows you to grab colors on the screen.  If you are a web developer this is essential.  It even allows you to save palettes.

2) ACDsee 10 or ACDsee 2 Pro.  Both of these programs beat the pants off of picasa.  I used to love picasa, and use it constantly.  The biggest issue that I had with it is that it didn't allow me to upload pictures to flickr without having to resize them.  I have a pro account, and this meant that I was wasting my money essentially, because I am paying for a backup of my original photos.  ACDsee has all of the features of picasa, and more, plus it does a better job at organizing my photos.

3) Keytweak: It allows you to change your keyboard keys.  I like to have a big control key, so I replace my left windows/apple key with ctrl

4) Yahoo maps: If you live in philadelphia you should use Yahoo maps,  the google maps has many streets wrong, and tends to lead you into bad areas more easily.

5) EmEditor: Best editor that I have found, thanks to Ben for pointing this one out.

6) Mobipocket reader: If you have a windows mobile phone then get this program, it allows you to read books on your phone.  But the best part is it has a windows program that keeps your notes and highlights in sync, so you can pickup where you left off on the computer.

I try to keep things simple, I do not like to complicate my life by installing more software than I need.  But if you have not tried any of the above programs, check them out, you may find them to be as useful as I have.