I just happened to notice that Sinatra has made it into Debian - awesome!
Looks like Merb is about there too:
libextlib-ruby1.8 - General Ruby 1.8 class extensions for DataMapper and Merb libextlib-ruby1.9 - General Ruby 1.9 class extensions for DataMapper and Merb libextlib-ruby - General Ruby class extensions for DataMapper and Merb
Thin is there, Rack is there, Ramaze, Camping, and Mongrel too. No Unicorn yet, but I expect it soon.
I'm curious about Spec and Nora... so many to choose from!
TODO: