For my son's 5th birthday he wanted an Astronaut party. I made invitations using Microsoft Picture It! I used the "swap face" feature to put his face in place of an astronaut's face floating in space.  I downloaded a NASA looking font (1001fonts.com) and typed NASA in large font, then "Blast off to Astronaut Charlie's 5th Birthday" Launch Date: XXXX, Launch Time: XXX, Mission Complete: XXXXX, Space Station: (Last name), Mission Control: (rsvp number). At the party, guests were welcomed with balloons tied to an art easel that said "Welcome to XXXXX(our last name) Space Center". Inside the house I had posters of space shuttles, astronauts and planets that I got from the local teacher supply store ($1.50/ea) and also was lucky enough to borrow a giant space shuttle poster from my dad who worked at NASA years ago. When the children arrived, they all put on their "space suit" which was a white t-shirt that I personalized with the NASA font and picture of a space shuttle. I made the iron-ons again using Picture It! I purchased plain Hanes t-shirts (undershirts really) from Target. The kids loved them, especially since each one had their own name on it. While guests arrived, they had "free play" in the playroom. I downloaded pictures from nasakids.com and made each child a coloring book. I had them on a table in the playroom with sparkle and glitter crayons to color with. I also had a table set up with a space shuttle puzzle that the kids worked on for a little  bit.  As kids arrived they also decorated "rockets".  Each child got an empty film canister. They decorated them with various space-themed stickers. Then we went outside and a grown-up helped with launching them. Each canister was filled with 1/4 tablet of alka-seltzer and then filled with water. Place the cap on, then place canister lid-side down in empty roll of toilet paper (set in playdough,so it won't tilt) and wait for the "launch". It was really fun to see how high the rockets could blast off! After the rocket fun, we moved to the garage where my husband and I had set-up "outer space" We hung black plastic tarp (from Home Depot) from the rafters in the garage so that there were 4 totally black walls. We taped glow-in-the-dark stars all around. I even had a glow in the dark ball that I hung in the middle like the moon. We changed the regular lights to black light and borrowed a strobe-light from a friend who is a dj. We blew up 100+ white balloons and just let them lie on the floor. I had wrapped treats in aluminum foil for "moon rocks". The treats were Starburst candies, Milky-Way candies, actual "moonrock-looking" superballs, "pop-rock candies", space themed stickers and pencils, and mini g-i-d aliens. Each child had a paper bag with their name printed with glow in the dark paint pen and a glow necklace, then they went on a treasure hunt for moon rocks. Each child was told to find 8 "rocks" and they were very good about following the rules. They came back inside and opened their rocks and traded so that everyone had at least one of each prize. For cake I made the "Space Cake" from FamilyFun.com and served Tang to drink. One of the presents my son received was "rocket balloons". THis turned out to be a great party activity. We were blessed with gorgeous weather in January (in the Seattle area that is rare!), all the kids were outside blowing up the balloons and letting them fly. If I knew the weather was going to be so great, I would also with their t-shirt, a glow neckace, a coloring book, "moon rocks" and a balloon. My son had a great time and even my 2 year old loved it and wants a space party for his 3rd birthday!