@Chuck: Season 3 is a good start. They're usually really good about covering any essential info / plot points in the flashbacks at the start of each episode.
@MadameDePompadour: It's basically a wildly inconsistent, sweary Welsh version of Doctor Who, with a side order of sex and violence. Episodes vary from face meltingly awful to pretty damn great. Thing is, the bad ones are so bad they're actually entertaining.
Children of Earth was great but I'm not sure it'd make sense unless you watch the first two seasons.
@Stochastic_Sam: Misfits is probably the funniest thing on TV at the moment. btw UK people can see the first season free on Ch4s website, or on Virgin tellys "On demand" thing. (foreign types may be able to use the website, or it may be ip locked like iPlayer, no idea..)
@ShanaLD: The first season of B5 is very hit and miss but if you can make it through that it starts to get really good, until season 5 which sort of fizzles out..