Harry Potter 8 year old-- My son Alex wanted to do Harry Potter for his 8th birthday.  We started with many ideas from this site, and changed them a little to make them our own.  The invitations were my favorite part-- we imported a Hogwarts crest from the internet, and printed an acceptance letter on parchment in green ink, worded exactly as Harry's letter was.  We scrolled them, and addressed them to each child's bed (we found out where each child slept in his house.)  Then we printed an owl coloring page, and my kids colored one for each child, we cut them out, and hung the scroll from the owl's feet.  I hand-delivered each owl and hung them from the front door while the kids were at school, so when the got home, it looked like an owl was actually delivering a letter to them.  When the children arrived, they had to run through Platform 9 3/4, which was a bedsheet with the Platform 9 3/4 spray painted on the top, and cut into strips from the name down.  We hung it over the front door, and it had quite an awesome effect as the guests pulled up.  Then they made their wands, which were dowel rods we cut down to twelve inches and spray-painted black. The kids decorated their own wand with star and moon stickers. They were then sorted into houses-- I used the suggestion of the walkie talkie in the sorting hat, and the boys thought it was great! I had gotten fabric of each house's colors and had sewn neckties for each child to put on as they were sorted. They had been asked to wear wizard clothing, so with their house ties, they looked very official.  We then had four activities-- one for each house which they rotated through. One was care of magical creatures. I bought a large cauldron from Target, and over the course of weeks I collected stuffed animals from Goodwill and garage sales until I had a bunch of stuffed magical creatures (I even found a three-headed dog for forty-nine cents!)  They had an instruction sheet as to what to do with each creature-- they tossed each of them into the cauldron in a different way-- from on top of their heads, backwards, while lying on their backs, etc. They wanted to play that over and over. Then we had Defense Against the DArk Arts, which was 6 witches' hats stuffed, and glow-in-the-dark necklaces made into rings.  They just threw the rings around the hats.  We had Divination, which was my sister dressed up as a witch, telling the kids their fortunes.  We set her up in a dark room with candles, a lava lamp, a magic 8 ball, and several books on palmistry we had checked out of the library. She really got into it, and the boys got a kick out of what their futures held.  The final class was Potions.  We had several experiments. One used cabbage juice.  I had laundry detergent in one cup and baking soda in one. They had to say a spell and add one to their cup, and I told them if they were harboring a secret, their potion would bubble over.  We did another potion with dry ice and bubbles. They loved waving their wands and making the potion smoke and bubble over. The ohhhhs and ahhhhhs were amazing!  We had a Quidditch game prepared, but it was really too cold out, so we then went to the Great Hall.  I had our dining room table set up extra-long so that everyone could sit around it. It was set with black tablecloths, and a punch bowl in the middle with smoking, bubbling punch in it (from the dry ice). I had found old sheets of each house color at thrift stores, and painted the name of each house, as well as the names of the boys who were sorted into each house.  We had punch and cake.  The boys were each given a bag, then, and invited to shop in Hogsmeade before their parents came to pick them up. I had bought bags of candy and given them names-- Dumbledore's Lemon Drops, Witches' Teeth (candy corn), owl pellets (chocolate covered raisins),  Bertie Bott's Every Flavor Beans, etc. They had been poured into bowls, so the boys could pick a few of each to put into their bags. They LOVED picking out what they wanted.  Their goody bags (which were promotional bags I got for free from our bookstore after their big promotion of the latest Harry Potter book) consisted of their candy bags, their wands, HP tattoos, Glow in the Dark sidewalk chalk, and Pop Rocks magic potion kit, which came with a small test tube to mix their potion in.  We had a great time-- and we had as much fun planning the party as we did hosting it!