I am not associated with Amazon. Shop around for the best deal. Here are a few ideas:

Transportation thick cardboard 48-piece floor:
http://www.amazon.com/Melissa-Doug-...p;ie=UTF8&qid=1285870124&sr=1-50

"Going Places" 48-piece floor:
http://www.amazon.com/Melissa-Doug-...p;ie=UTF8&qid=1285870152&sr=1-63

Classic cars 100-piece:
http://www.amazon.com/Classic-Cars-...mp;ie=UTF8&qid=1285869539&sr=1-5

Some Pixar Cars 48-piece puzzles:
http://www.amazon.com/Disney-6663-P...mp;ie=UTF8&qid=1285869539&sr=1-9

Disney Pixar Cars Lightning McQueen 60-piece plastic puzzle sphere:
http://www.amazon.com/Disney-Lightn...p;ie=UTF8&qid=1285869709&sr=1-40

3-D motorcycle sidecar wooden puzzle:
http://www.amazon.com/3-D-Wooden-Pu...p;ie=UTF8&qid=1285869539&sr=1-24

American Express Train 114-piece wooden:
http://www.amazon.com/American-Expr...p;ie=UTF8&qid=1285871057&sr=1-21

Trains 100-piece (weight of 2 pounds indicates it must be big or substantial IMHO):
http://www.amazon.com/Trains-Piece-...mp;ie=UTF8&qid=1285870666&sr=1-8

Eagle Canyone Railway 200-piece:
http://www.amazon.com/Melissa-Doug-...p;ie=UTF8&qid=1285870923&sr=1-46

Thomas glow-in-the-dark thick cardboard 100-piece (plenty of other train ones are linked starting from that page):
http://www.amazon.com/Thomas-Carnival-glow-dark-puzzle/dp/B000B8THDC/ref=pd_sim_t_1

Thomas thick cardboard 60-piece: http://www.amazon.com/Thomas-Friends-Goes-Piece-Puzzle/dp/B00005CESR/ref=pd_sim_t_2

Ravensburger construction 60-piece:
http://www.amazon.com/Ravensburger-Construction-Crowd-Piece-Puzzle/dp/B000NYPDIC/ref=pd_sim_t_9

Ravensburger fire department 100-piece:
http://www.amazon.com/Ravensburger-Fire-Department-Piece-Puzzle/dp/B002EZZ6N0/ref=pd_sim_t_10

Fire engine 67-piece construction kit (maybe you can find similar kits along the line of trains or cars):
http://www.amazon.com/Fire-Engine-W...mp;ie=UTF8&qid=1285870218&sr=1-1

Ah, here's one (steam train wooden puzzle/kit):
http://www.amazon.com/Steam-Train-W...p;ie=UTF8&qid=1285870334&sr=1-29

Matchitecture antique car (I know this is more than 48 pieces, but looks interesting and I'd give it a go, personally):
http://www.amazon.com/Bojeux-b6616-...p;ie=UTF8&qid=1285870411&sr=1-30

Antique car wooden kit:
http://www.amazon.com/CE-made-in-Ta...p;ie=UTF8&qid=1285870411&sr=1-46

Striving to increase my rate of flow, and fight forum gloopiness. sick