Oh yeah, the bases for these are from WotC Flash Speeders, I got a bunch back when they were cheap, and I've been using them for all my landspeeders.
Gian Sport Speeder
The first one is a modified Gian Speeder, from the old Galoob Action Fleet toy range. I removed the side-mounted guns to make it look more like a civilian vehicle. The original model was a long, 4-seat model, and I wanted this one to be a 2-seat racing vehicle. So... I got out my razor saw and cut out the center section with the rear seats, then glued and filled the gaps from the join. The end result looks a lot more sporty, and after a bit of sanding the join ended up being almost imperceptible. The driver next to it was a WotC Star Wars character, I cut off his hand and added a nice cool beverage. Thanks to my wife Debs on this one, she did most of the painting on the speeder and the driver.
"A-1 Deluxe Mobquet Floater"
The second one was a more complicated model. It was based on an old plastic toy car from the 1950s that I found in a flea market from a company called "Wannatoy." I noticed that it looked a bit like one of the speeders that can be briefly seen in some of the Mos Eisley background shots in Star Wars. It got my imagination going, and I decided to try to convert the toy into this speeder. A bit of internet research discovered that this vehicle was called an "A-1 Deluxe Mobquet Floater", and there were even the original blueprints available from when the built the prop! (see below) Isn't the internet amazing? Armed with the plans and a few photos, I set out to create my version, loosely based on the original.
I lost all my in-progress shots, but here is a picture of one of the same toys from ebay:
In the movie:
The bottom of the toy had holes for wheels, and I filled these with plasticard and putty. I then added the 2 seats inside in tandem, and a custom driver with a sculpted helmet, goggles, and breathing mask. The side engines were just plastic tubing, cut and glued onto the side rails. The dorsal fin in the back was a piece of plasticard, cut and pinned into the rear of the vehicle. The actual prop had 4 fins positioned like the rudders of a torpedo, but this looked like too much work, so I just stuck with the one.
The last, and most difficult bit was the canopy. The rear (opaque) section was made from bronze putty, formed around a marble and popped off when dry, to get the rounded shape. This I glued on and filled. The clear section was a blisterpack form from an oven-light bulb that I got at the hardware store - the packaging was just about the right size, and when carefully cut down it fit pretty closely. It was glued into place with 5-minute epoxy, and then I added the curved slats by using very thin plasticard strips, bent and glued again with 5-minute epoxy. I used epoxy because superglue would dry too fast to position correctly, and it would likely fog up the clear plastic. Final weathering touches and the "A-1 Deluxe Mobquet Floater" was complete! It is not an exact match, but it is close enough for me.
At this point I have 11 completed speeders, more than enough for the race.