Baseball party. My son just turned three and we did a baseball theme at our local Little Gym.  We used a glove/ball invite that read "Carson rounds second and slides into third...Please join us for a grand slam celebration" For the RSVP we said "strike outs only".  I used a sport postage stamp with a baseball seal on back. Since we were doing it at a local gym we had to keep decorations to a minumum (we only had 10 minutes to set up).  I made a sign on thick art board that had my son's picture playing with his bat and ball and it read "Carson is safe on third". I had this at the entrance along with a baseball bat engraved with his name ($5 from oriental trading company) for people to sign.  I found 4 huge fabric blowup baseballs that they let us put in the gym during play time (walmart). I had cut out baseball players for the windows (double sided).  I coordinated with the instructors to do baseball activities during the play time. My son and his little brother wore matching baseball shirts.  I decorated the tables with green table cloths with huge white napkins to look like bases. I put a Home Base at the spot for my child to sit.  And sprinkled baseball cards down the middle.  I found baseball plates and bought my cake from Price Cosco (got rave reveiws).  Everyone thought the cake was from a some special bakery. My secret is to order cream cheese frosting for the middle and top and chocolate cake...delicious. I had snacks set out during the party... red vines, peanuts, pretzels, water, gatorade.  My favors were bright colored baseball hats with each childs initials on them.  I found the hats at oriental trading and and the letters were iron ons from a local fabric store. I loaded them up with baseball treasures such as sports fruit snacks, cracker jacks, gum, baseball cards, whistles, baseball puzzles, plastic baseballs, blow up beach baseball, suckers, etc.  I put these into a popcorn bag (found at a local party store) and turned the hats upside down and placed them in the hat.  I found a baseball font on the computer and printed their names to personalize them even more.  I also had stuffed baseballs for the guests under 1 year of age.  For the adult party favors I used baby ruth candy bars and put "It was a grand slam, thanks for playing". The party was a great time and I even found cute baseball note cards (chelsea papers) with my childs name printed on top to use as thank yous.  The party was simple and a lot of fun to plan.  It is pretty easy to find baseball items. My best advise is to choose a theme that is readily available. Have fun!