We had a great birthday for my son - he chose what he wanted a zoo theme. All the kids met at our house for animal cake and ice cream, then we took them all (along with any parents that wanted to join us) to the local zoo for the afternoon. The kids had a great time viewing all the animal with friends. My son made each of the guests a small trinket box with a animal that he thought each would like on the top.  (he used the small wooden boxes that you find at craft stores and the small flat wooden animals that are around 25 cents each). By his request he asked for books to be given to his school library - so the next Monday he brought in 16 books to the library.  We do not have tons of extra toys and the entire school benefits.  Invitations and thank you cards were made with animal die casts made at the local scrapbook store and were written as a zoo adventure.