Boys:

• This can be much easier than you think. Just buy Halloween costumes for a superhero or two, or from a favorite cartoon show. The biggies, like Batman, Spiderman & Superman, are available year-round at BuyCostumes.com. Take some time and browse their site, though, and you'll also find things like Harry Potter, Power Rangers, Dragonball Z and Yu-Gi-Oh. Another great site to use to find costumes for famous characters is CartoonCostumes.com.
• If you'd like to set him off on some medieval adventures, Hearthsong has Knight Costumes, and wooden shields and swords in its Dress-Up Clothes and Accessories section.

• First of all, there's no reason why you wouldn't want to use BuyCostumes.com and CartoonCostumes.com to find stuff for girls, too. Also, the Dress-Up Clothes and Accessories section at Hearthsong has some Princess-type stuff, and butterfly wings. Another idea is College Replica Cheerleader Outfits from OnlineSports.
• DisneyDirect.com has very nice dress-up outfits for the Disney Princesses ... Ariel, Belle, Cinderella, Jasmine, Mulan, Sleeping Beauty, Snow White ... and others like Tinker Bell

Medical Clothes:

• For pretending to be doctors or nurses or other medical professionals, check out Nurses Station for scrubs and uniforms in youth sizes, sometimes they have fun prints like Finding Nemo ... or try AllHeart.com for kid-sized scrubs featuring characters like

Sports Uniforms:

• SportsFanfare.com has youth replica team uniforms (jersey, pants & helmet) for NFL teams

Furniture for Pretend Play:

• Aesop's Room - play kitchen appliances made of wood