Before I returned my Treo 750 I had loaded it up with programs that I had used over the years on my various Windows Mobile PPCs and phones. Many of them wouldn't work on the square Treo screen, but some did and for those new to the 750 I'll mention them so that you can try them out.
One of the best software houses for Windows Mobile is DinarSoft out of Canada. I've used four of their programs for years and years and am a big fan. The first is HandySwitcher.
As you know Windows Mobile doesn't close programs so you can easily bring your 750 to a halt with all those open programs running in the background. HandySwitcher manages them, lets you see what's running and allows you to close open programs easily.
The icon you see in the picture above is customizable - it can be moved to the left or right, or can be put in the tray at the bottom of the screen. It also integrates nicely with two other programs by DinarSoft that I will be talking about later - HandyMenu and HandyLauncher.
I have tried a fair number of freeware programs that do the same thing, but none are as customizable and a fair number of them have led to instability of the OS. By the way, I've been using these programs long before I became an Associate Writer here and have bought and paid for all of the ones I'll be talking about.
HandySwitcher costs $9.99 and can be found here. There is a trial available. Highly recommended.