any advice or recommendations?
If you're talking about hostels, I can recommend StayOkay VondelPark in Amsterdam. Easy to get to, close to everything and in a fairly quiet neighborhood (right next to Vondel Park).
Can't speak for Brussels. Have you tried looking at hostel reviews on hostels.com and eurotrip.com?
On this site, under "graffiti wall" (at the top of this screen) there is a topic "Best European Hostels". Individuals can enter their experiences/opinions. I think the third entry down is a gal, Bev, from Yorba Linda, who stayed at a hostel in Amsterdam the end of May. Check it out. Have fun on your trip.
I second the StayOkay in Vondelpark. The breakfast is really good by Dutch standards. You might also want to consider a botel in Amsterdam. There are tons of little houseboats turned hotels that offer affordable rooms and you get a particularity Dutch experience out of it. We have stayed in two botels and I found them both on hostelworld.com, but I am sure a google search will turn up more options.
I've also stayed at Vondelpark hostel. It was a decent hostel.
I haven't been to Brussels yet so can't give advice for that.
I have found that for Brussels you might be better off in a hotel, especially if you are going to be there over the weekend. We have stayed in hotels both times we were in Brussels because it was cheaper (for two people) than the available hostels.
2GO4 was a nice hostel in Brussels. It was convenient to the train station and to the downtown areas.
Brussels is a great city for Priceline. We got the Radisson SAS last May for $60. Have a great trip!
I've heard that the flying pig in amsterdam is good- that's where I'll be staying!