I've tried 3 different foam cannon with my pressure washer (by major name brands) and was disappointed with them all. Either they were way too loud or didn't make enough foam. I finally found one that was real good, powerful, made a lot of foam, AND was pretty inexpensive (compared to Adams, Chemical Bros).

I have no affiliation with the company at all (I promise), but I found this Rydell foam cannon and paid under $50. Now it's on sale for $37.97. Yes, I'm a little pissed that I didn't get it at that price, but I've emailed them and asked for a refund of the difference (fingers crossed!). Either way, it's definitely worth the $38 bucks.