Oh, lots
eBookwise (sold it to buy a Sony)
Sony 505 (sold it to buy a Kindle 2)
Kindle 2 (gave it to my aunt, bought a Kindle 3)
Kindle 3 (gave it to my aunt when her husband stole her Kindle 2)
Kinde Touch (sold it when I thought I could get by with just an iPad)
Kobo Glo (when I got wrist problems from over-using the iPad)
If Kobo ever makes a Glo Mini, I would probably sell my Glo and get that. I also have an iPad Mini I use sometimes, which I sync with my iPhone. I tend to keep mostly short story collections on it because I can read those on the Mini during work breaks, or on the phone while commuting, and they aren't difficult and I can finish a story in one session. I do most of my longer leading on the Glo.