My little sister was turning tweleve and asked me to help plan her birthday party.  Since she was going to invite both boys and girls to the party she decided on having a Harry Potter theme.  For invitations, I found clip art of a wizard who looked a lot like Dumbledore and placed it on the cover with the words in blue; You're Invited. Then, inside I hand wrote in green ink a letter of acceptence to Hogwarts School of Witchcraft and Wizardry.  I bascially wrote as it is in the book and simply included the time and date of the party.  Also, I included that the "students" should bring their own brooms. (This was for a game that was to be played.) For decorations, I made a sign that had owls carrying letters and the Hogwarts express and it read platform 9 and 3/4's. This was so the kids were "entering another world" when they entered the house.  For the party room, I seperated the space into four sections.  One for each of Hogwarts school houses.  I used red balloons and streamers for Gryfindor, blue for Ravenclaw, yellow for Hufflepuff and green for Slytherin. I also made four signs, each with a house name and the house animal.  (Gryfindor is a lion, Slytherin is a snake, Hufflepuff has a Badger and Ravenclaw is an Eagle.) I place a sign in each of the houses corner. I took some pingpong balls,painted them gold and hot glued two feathers on them.. I attached to them some fishing wire and hung them from the ceiling. The kids enjoyed their "flying" snitches.  I used plastic purple tablecloths, Harry Potter plates, cups and napkins and gold moon and star confetti to decorated the tables.  Child size witches hats made cute centerpieces.  The cake was a Harry Potter cake from the local bakery. For the games: first I had cards with the different house names placed into a witches hat and then each child was sorted into his or her house. Once the teams were established I exlained the rules.  Instead, of winning prizes at each of the games they would be winning points for their house. Each house had the goal to get 500 points so they could go shopping at Honeydukes.  The first game played was pin the tail on Mrs. Noris. I was funny seeing that cat with over 10 tails.  Next, was hunt for the snitch.  I hid several ping pong balls with different points written in permanant marker and one ball, hidden very well, was painted gold and worth 150 points.  Then, the kids got to use those broom they brought and played Quditch.  (Actually, hockey with broomsticks using a soccer ball.) Then, it was time to battle the dragon, like Harry did in the fourth book, only this time it was a dragon pinata. Last, we have a very competitive game of Harry Potter trivia, based on the movies and the books. I had a chalkboard to keep track of the kids scores and made sure each house won in the end. For Honeydukes I had a table set up with sign with the name Honeydukes and differnt pictures of candy found in the wizarding world. We had chocolate frogs, (gummy frogs dipped in chocolate) cauldron cakes, (cupcakes) cockroach cluster, (chocolate covered pecans and brown sprinkles) licorice wands, (chocolate dipped licorice). Also, I painted a golden snitch on a jar and filled it with Bertie Bott's everyflavor beans, (jelly belly's)  The child with the closest guess to how many were in there won the jar. Finally, for favor bags I used purple plastic goody bags, to match the table cloths and filled them with frog poppers, glow sticks(portable wands) and silly cardboard glasses. I also made each guest a Hogwarts report card by soaking some paper in tea, to give it an aged look, and giving grades for transfiguration, potions, charms, quditch and herbology. All A's of course. It was such a fun day and many of my little sister's friends are now saying they want to have a Harry Potter, too!