I came across pseudopod first - it's debut was linked to from the Tables of Malcontents blog on Wired, back when it still was in its old incarnation run by Lore Sjoberg. I joined Psuedopod, then after a while decided to check out Escape Pod as well - this was around episode 80, I think, but I went back and listened to some older ones as well (I still have a lot to get through, maybe once I finish my dissertation and have some free time I'll order a disc).