If I am listening to all my music and I hear a song and I think it would be great to add to a certain playlist (lets say a playlist i called "gym mix", is there anyway to do this from the iPod touch itself, instead of having to remember this and them do it from iTunes when i am at my computer. This seems like a basic function but i can't find it anywhere
Assuming you're running the latest iOS:
Select a playlist. Select "Edit" from the buttons at the top of the playlist under the search field. Tap the "+" in the top left of the toolbar. Find the song(s) you want, and hit the "+" to the right of their name. Tap "Done" when finished.