I’d suggest Rokenbok cars. They’re radio-controlled cars that can have up to six cars on a base. The pick up stuff and dump it and they’re compatible with Legos. My sister got lots of them for my niece. I think we had as much fun as she did.
StG
You guys are sooo behind the times. What he wants is the new generation Hide and Seek toy.
Its on my to-get list. 
We do have a K’nex set that I scored BIG FOOKING time at a garage sale for $5 . (YAY ME! and it’s n ot a complete set, but who cares?!) and he and his sister do enjoy playing with that from time to time.
Her favorite thing to do is make Girl Robots.
What’s that sound?
Oh, it’s a feminist weeping.
We do have a marble run (actually two) because of the joys of garage saling and scoring in the same day the exact same set for a total of $10. Yeah, those are very good times!
One thing that I just found that I love and it is growing on the kids is Kapla Blocks Very cool different take on blocks. I love blocks.
Legos…huh…I don’t think anyone here has mentioned legos.
What do you all think of legos? Anyone? Buellar?
I was thinking of cd-rom games like Tetris ( Hey, I’m old school)
Cube Burst looks kinda cool too.
Also:
I have an eight year old boy, and though I like to think of him as “different” from the herd of common children, I think he would love to go paint ceramics!
Aesiron, perhaps?
And I put in a vote for Lego, too.
Bah. I hated Legos as a kid. Boring.
Hot Wheels though, that’s the stuff. I don’t know any 7-year-old boy who doesn’t love 'em. I loved 'em as a kid. I gave hot wheels sets to each of my nephews when they were 7 or so, and they loved 'em too.
Another vote for Legos. Best. Toy. Ever. Especially when he discovers the joys of blowing his toys up w/ firecrackers, as all boys are wont to do. With legos, you can put em back together again! (That is, if you manage to find all the pieces).
You mention he loves trains. He has a Thomas the Train? That seems a bit under his age, maybe its time he upgrades to a REAL train set?
Some other ideas… rubberband powered planes, Capsela (those can be expensive and hard to find, I still weep over not getting the Capsela set I wanted so badly as a child), Erector Sets (do they still make those?).
Since he enjoys trains, how about a model train set (Hornby or equivilent) or a Scalextric set so you could all race cars? That way, everyone is happy.
My son has been attending 6th birthday parties almost every weekend lately and I’ve been getting every kid this Mutant Freak Creature head thing and some goop. It’s been well-received. I’m sorry I can’t find the Mutant thingy online, but they sell it at Target.
I personally would suggest a party where the kids could burn off their , as my son says " tough energy" rather than ceramics painting. Bowling might be good or a gym or swimming party at the Y. We did karate for Kindergarten Caricci and we’ve done a McDonalds with the big climber and a place like Chuck E. Cheese too. We gauge the fun by how plastered with sweat my kid’s hair is to his head .
Yeah, the ceramics thingie is forgotten as we are going to a Chuckie McPetrie Dish Cheesies tomorrow for a party. :::::::::::shudder:::::::::::::::
A really fun, fun gift that wears the kids out (if you have a park or a big back yard) is bStomp Rockets Great Googley Moogley is that ever an entertaining toy for all ages! And under $15. Good times.
One thing about Hot Wheels:
If you were to get Hot Wheels, I wouldn’t just get track. I’d also get one of those power stations (I forget what they’re called) that uses two fast-spinning rotors to shoot the cars along the tracks.
For anyone interested, I scored a Foosball Table in excellent condition at the Salvation Army for my son’s birthday.
Cool and old school.
Am I da bomb or what?