Firstly, [i]and I'll be expecting flak from other peers over this[/i], I personally don't like using MSCONFIG mainly because it is not instantly accessable. I much prefer to use WinPatrol which resides in the SysTray and can be accessed with a single mouse click. It also caters for a far wider range of low-level examinations than msconfig could ever achieve.
It also gives you a warning via a small on-screen pop-up, whenever a program attempts to add itself to your msconfig file, giving you the option to approve the addition or not. Msconfig cannot give you any warning at all, so you never know what is in it until you go in and have a look.
http://www.winpatrol.com/download.html
//End of rant//
Secondly, given that every user tends to have a slightly different computer and a varied System32 folder, your best bet would be to elect to take one msconfig entry at a time and Google it in order to find out for yourself what it actually does. Peers from TR cannot realistically tell you what you can "safely uncheck" because, if they are honest, they don't know what files populate your msconfig listing - only you do.
Edit for typos.