Oh neat, I'll have to check out some of yours later. I'm following:

ctrlcreep: not a bot, but only writes short sci-fi/dystopian story bits/prompts
mythologybot: generated excerpts from fake archives-- sometimes pretty much exactly what you'd see in an actual museum on an info card, sometimes kind of wild
yearonearth: live tweeting the history of the earth compressed into a year-- sparse tweeting right now as we're still in Huronian glaciation
oewordhord: Old English Word of the Day

ETA: also if you like bird photo bots, a friend of mine retweets from _everybird_ a lot, it's just going through every (known) bird on the planet with a photo.