I heart series! I do collect and or read a lot of series. Because of the state of my TBR pile I have collected a lot I haven't yet read. I definitely use the series feature on Librarything, I think it's just fun to look at! According to it I have 86 series covering 149 books. It has actually clumped together books that I didn't realized were considered series! My series range from fiction to chick lit to young adult to art to comics! I think two of the largest series I have are the Best American Short Stories and Harry Potter and the largest that I don't own is A Series of Unfortunate Events (I still haven't read the last 2-3 books and at this point I think I should just start over!) The feature is also helpful to figure out the order of a series if I'm unsure!
How about you, are you a series person?