I've been rather surprised at how little, comparatively, the last Congress achieved, considering that both houses and the presidency were in Republican hands. I presume this is because Iraq has severely distracted everyone's attention, but Clanad may be able to put me right on that. I don't think having a congressional mixed marriage is necessarily a recipe for gridlock, though; America has coped with such things before, as you point out, Stu.
Anyway, one of the independents was Joe Lieberman, who was previously a Democrat (and a vice-presidential candidate) but was, in UK terms, deselected by his party this time round, apparently for being too pro-Iraq war. So he ran as an independent, running against and beating the official Democrat candidate, but has said he will vote with the Democrats anyway. In essence, it's the same principle as a coalition government, though those are more common in countries with some sort of proportional-representation voting rather than the first-past-the-post system used in the USA and UK.