Ok so Rails is the must have framework, and Mongrel the must have server. But may be you just had an error when trying to launch Mongrel on Debian and you are googling desperately for a solution.
So, if after typing:
uninitialized constant Mongrel::HttpHandler (NameError)
The reason on Debian might be your Gem package is outdated, so try to type:
sudo gem update --system
For me this upgraded Gem from 0.8 to 0.9, than I reinstalled Mongrel with:
sudo gem install mongrel --include-dependencies
sudo gem install mongrel_cluster --include-dependencie
and voilà, Mongrel is now working!
Hope this help.
PS: Viva Lula! viva Chavez! fudeu a direita! Com mas de 60% dos votos contra direita, foi uma boa goleada contra burguesia, valeu. (translation: no putsh in Brazil neither Venezuela, South America is going fine).