Here's a bunch from Parenting.com:

http://www.parenting.com/article/Child/Activities/A-Pie...-Cake!-1200668181032


And from Parents Magazine:


www.parents.com (of course!): the site will literally plan your celebration for you. The Birthday Party Planning Tool asks a series of questions and then generates a complete list of party ideas

www.einvite.com: for professional-looking invitations. Search "print at home." Buy the design of your choice and make sure it has the "Easy Invite" logo. Then, follow the instructions on www.easyinvite.com to lay out your text.

www.music.aol.com: to play free kids' radio.

www.freekidsmusic.com: download songs from here to create your own playlist for the party

www.thekidzpage.com: to use free clip art for invitations and decorations. Repeat the image on invitations, labels for cups, goody bags, cupcake flags and a "Happy Birthday" banner

www.kidscraftweekly.com: for hundreds of affordable craft projects