There has been a thread on this recently, so a search might be rewarding. Otherwise use Google to check what the processes are, and common sense to decide whether you need them. CCleaner won't help, by the way, apart from being an easy interface to the startup list.
I think the important question to ask in this situation is... Are you having symptoms or problems with your computer that would make you think there's something wrong? Or are you just exploring and trying to learn?
If there are symptoms or problems with your computer, I'd suggest reading this thread FIRST: Before you post! and then posting a thread in the Spyware Hell section of the forum.
If you just want to learn more about the processes running on your computer, Process Library is a good resource as well as any search engine like Google/Yahoo.
I can help you I think with iTunes stuff. If you have an iPod, the only service you need to have is "iPodservice". Unless you have an iPhone or iPodtouch, you don't need anything else running.
You can safely get rid of the "Bonjour" service, Itunes Helper, Apple Mobile Device Service, Quicktime Task, and AppleSyncNotifier.
And I would suggest setting the iPodservice to manual, otherwise it will run all the time.
Start\Run\Type "services.msc" (without quotes). Right click iPodservice and select "properties", and under "Startup Type" select manual from the dropdown menu.
This service will start when you launch iTunes, and that's the only time you need it.
My daughter has an iPod Nano, and it syncs and updates fine with that one service running.