Despite a little too much hype for my tastes, a quite useful site for figuring out what is going on inside your PC: ProcessLibrary.com – The online resource for process information:
In the recesses of your computer, 20-30 invisible processes run silently in the background. Some hog system resources, turning your PC into a sluggish computer. Worse yet, other useless processes harbour spyware and Trojans – violating your privacy and giving hackers free reign on your computer. ProcessLibrary.com is an invaluable resource for anyone who wants to know the exact purpose of every single process
Could be useful.