I'll concentrate on the Clone Wars vehicles:
Revell do a nice 1/72 Republic gunship that will look good with the WotC minis. Revel are also bringing out a 1:50 AAT tank and a 1:88 AT-TE walker that should fit well. Can get expensive quickly though.
Star Wars Transformers toys. The Droid AAT tank is a reasonable size, some of the starfighters may be close too. The republic gunship is probably too small for 28mm figures, but I didn't care – they're "good enough" for tabletop gaming (especially if they spend most of the game up on flight stands). That looks like one in the link you provided. The clone wheeled tank is, IIRC, way too small. Cheap as chips on ebay.
Action Fleet vehicles are another source, many of them fit well with 28mm figs. I have a couple of the AT-TE walkers, but they really are too small for the WotC figures – they'd be better with 15s, or even 10mm. Again, cheap on ebay.
Don't be shy about using the WotC vehicles. The Hailfire Droid and Giant Crab droid are a decent size; the Corporate snail tank and Homing Droid are too small but (especially for the homing droid), work fine on the table. The clone ISP swamp speeder and AT-RT scout walker are OK. VERY cheap on ebay for the commons; stupidly expensive for the rares.
Hasbro Titanium vehicles are kind of scaled to fit the packaging. I've found that the Dewback is about usable with the WotC figures. Speeder bikes fit if you can squint (or replace the rider with a WotC scout). Nothing else is even close.
There was a WotC boxed set came out a couple of years ago that contained a Hailfire Droid, ISP speeder, clone and droid speeder bikes (unique to that set) and a dwarf spider droid. It also had Mace Windu and Greivous. That's a pretty good start for any Clone Wars vehicle collection.
Hope that helps.
comes up with the stats and roster for the Rust Devils in his sci-fi campaign.
