I just started watching Fifth Gear from the first epsode and thought it was pretty cool, load of format changes, but indeed, good to watch between the Top Gear Gaps.
Seen all FG's now, so I started watching Top Gear America which is, really, not at all bad. You get attached to the guys pretty quickly, really.
TG Australia is genuinely shitty, don't bother.
Then there's Wheeler Dealers, which is sort of cool. The presentation is a bit lame, but I like the technical aspect and background info.
And then I watched chasing classic cars, which wasn't bad either.
And Fantomworks, which is a nice, professional car repair shop with interesting customers (and a hot secretary girl, to boot).
Also, the stuff the Top Gear Guys made solo, especially May, is pretty epic. Including the Beer & Wine Series by James May and Oz Clarke. Great fun, and an old Jag.
Then I ran out of those, and started watching Stephen Fry and Robbie Coltrane's shows.
And then, downloading every single Top Gear episode and watching them from start is actually quite nice.
It's fun to see the show 'come together' througout the years, even though the first series, without May, is quite boring.
They do jump a bus though.
So, that should keep you occupied.