My daughter like most is crazy about Harry Potter, so we naturally needed to pull off a party. Because this was planned several months in advance (without her changing her mind !)  I set to work in secret so all would be a surprize for our daughter.  First the costumes for the guests. I found black fabric for a dollar a yard and made small robes. I also found 1.00 per yard red fabric and yellow fabric which I cut into strips then sewed them together for mufflers.  Next school supplies so the students could take notes.  I purchased dyed turkey feathers of red and yellow, cut off the ends and glued pens inside for quills. I found some Dragonhide note books at Scholastic book fair sale. All of these supplies were given to the students upon arrival.  The invitations invited future students of Hogwarts to a Griffindoor sponsored Hogwarts day camp. Further instructions told the guests to dress in muggle clothing since the day camp would be held in a muggle neighborhood. First class of the day camp was Charms where each student choose a wand.  ( dowels cut into 12 inch lengths, "sharpened" with a band sander, and stained a dark color)  We gathered in the common room and the head teacher for the day went over the class itinerary. When one of the childred said that nothing was written on the paper, she held it over a candle and the words appeared.  (Lemon juice works well for this trick. One of our "professors" taught the childred the incantation for levitating a turkey feather. As she said the words the feather danced into the air (with the help of invisible fishing line). The students began practicing on their turkey feathers with not much luck but low and behold a barbie off in the corner of the room began levitating. (this got them guessing) After charms the students pocketed their wand and went upstairs for herbology. Each was given two small pots.  They were told histories and legends of several different seeds. They then choose two seed types and planted and watered their seeds. Then downstairs to the dungeon for potions.  The students entered the room and found it darkened except for candles ing the fireplace and small lights in the corners of the room shinning towards the ceiling for affect.  There were jars of shells,bubbling jars of colored liquids on table tops and dark fabric draping everything.  The students were instructed to sit at two low tables (coffee tables).  There they learned to make love or cootie potions.  (I took the Koolaid recipie and adjusted it for a 4 oz cup.  Love was cherry flavor and cootie was lime.)  Dry ice was added and the students took out their wands, said and incantation and drank their potions. Then we had lunch at the Griffindor table. After lunch the students went to Defense Against the dark arts where they made troll boogie slime to help them ward off trolls. (white glue, borax, and water mixed in a baggie). Bach upstair for divination where they made crystal balls (jars with oil, glitter and water) and recieved mood rings. Finally off to quidditch where they took turns with a blugger and wacked the snitch. (I found a yellow sunchine pinata, stripped it of coloring, sprayed it gold, added jewels, and golded netting). Finally upstairs for desert which consisted of a two layer rectangle cake make into the quidditch pitch complete with goal posts and paper viewing towers.  It may sound like this cost a bunch of money.  However the planning and the set up was most of it.  Each student did leave with a robe, scarf, wand, quill, journal, ring, turkey feather, pots with seeds, troll slime, and crystal balls.  However each gift item was 1.00 or less and the decorations did not cost anything since I had all the stuff lying aroung.    This party was several years ago, but my daughter still talks about it and every year since she keeps asking if she can have another Harry Potter birthday. The frends that attended the party come over and still bring their wands, scaves and robes (albeit they are getting quite snug ;). Thanks for letting me share.