Check out Jeremiah by J.Michael, the creator of Babylon 5. Everybody who's gone through puberty catches a disease and dies, leaving just the children alive to fend for themselves. The show is set 15 yrs after the Big Death. Good stuff.
Journeyman is great, as mentioned. And actually rose above its premise. The 4400 was a fun ride while it lasted.
Torchwood and Primeval on BBC America are fun too.