Add yours here . . .
Recently I've watched the first epsiodes of Angel and Lost again. Both pretty cool shows but it was interesting to note that:
A) The vampire that Angel dusts in 0101 is played by James Ford who plays Sawyer in Lost.
B) The pilot who gets killed in Lost's pilot (pun intended) episode is psychic-boy from Heroes.
Now, (and I guess people may have already picked up on my examples, but let's roll with it . . .) add your own.