Roger & Mark live at the corner of East 11th St and Avenue B. The neighborhood has been gentrified since the era of Rent. Make sure to click on "Photos" in the upper right corner for some interesting images of what the neighborhood looks like now.
A short history and description of the neighborhood.
A site, appropriately titled Filthymess.com. Most of the pictures from the "Street Filth" section are from Alphabet City
The "Alphabet City" Flickr Stream. Some very interesting images of people and architecture.
"Art and Urban Space: Rent, The East Village, and the Construction of Meaning" is about how Rent is very much a product of its geography. Make sure to read this one - it's very useful.
Ephemeral New York: This deals with the history of NYC, but with a little hunting, there's a lot on the Lower East Side of the late 80s - early 90s.
Pictures of weird signs in Lower Manhattan. Just a little more neighborhood color.
Here are a couple of good entries - fliers from Save The Robots (an after hour club in Alphabet City) and 8BC, a club mentioned in "La Vie Boheme." "Avenue B - The Place to Be" was an annual music event.
Interview with Michael Stipe of R.E.M. where he talks about sex, drugs and coming to New York City in the 1980s. It's a few years before Rent, but he paints a very vivid picture of the art/rock and roll scene happening at the time.
A study of homelessness in NYC in the late 1980s: A bit dry, but very thorough...