The Weather. saves me from checking ther weathernetwork everytime i wanna go out. maybe the iTunes remote (the round one, not the default one), but i'm kinda interested with Synergy - less clutter.
Konfab is great at first, I used it for a month, but they start to get annoying. I eventually find that I can use iTunes in the mini state and look out the window.
I use the weather one, an analog battery gauge (looks like a car gauge), and an uptime meter. I did have a CPU load widget, but that itself slowed my machine drastically.