I really enjoyed being Team Parent. Basically, it will depend a lot on who the coach is and how organized they are, but at the T-ball level, you would probably be very much appreciated for things like:
1 - A contact list of all the parents phone/emails. You generally get these by passing around a sign up list at the first parent meeting and then at practices. The coach can give you a list of the players to begin with so that you know you have everyone. An email list is especially helpful when there are changes or information that need to go out.
2 - Snack sign up sheet for game days.
3 - Make sure everyone gets/signs waivers, forms, etc.
4 - Make sure everyone gets picture packets when they come in.
5 - Offer to help with the end of season team party and trophy ordering. Usually, you also gather $$ from all the parents for trophies and to put toward a coaches gift. Sometimes there are assistant coaches as well who get smaller gifts. Normally it's around $10-$15 per family, but it will depend on what the cost of trophies are, etc. Once in awhile, you'll find a coach that wants to purchase the trophies so the parents don't have to pay for them, but in my experience, that is rare. :-) As far as coaches gifts, I usually did gift certificates to a local sports/athletic gear type store.
These are just the things that I did, but each Team Parent does things differently. Sometimes a coaches wife will step in to do some of this stuff, too. Hope this helps.