I'm somewhere between a magpie and a gorilla - I tend to only read in a small group of fandoms at one time, but do pick up new ones and discard old ones as the fancy takes me. It's just that the fancy takes, like, a year to change at minimum. When I think back to starting in fandom, it was Star Trek (via a.s.c.e.m. and if you know what that means you're old-ish in fandom), and then Buffy brought me onto the web. But neither one of those kept my attention for all that long. Since then I've wandered through Hercules, The Sentinel, Due South, Harry Potter, and a slew of other smaller and larger fandoms. SGA probably claimed my attention fastest of any conversion, and I think that was just due to the sheer mass of highly entertaining content.