Ruby 1.9 on Heroku
Heroku just pushed their new deployment stacks to public beta. You can now run your Heroku apps on Ruby 1.8.7 and 1.9 (as opposed to the old standard: 1.8.6).
To test this out, I whipped up Ultraviolence, a quick wrapper around the Ultraviolet gem. Ultraviolet will syntax highlight text, using parsed Textmate bundle files. Any language that Textmate supports will work, using any theme that Textmate supports.
There's also a web api if that's how you want to roll...
I chose Ultraviolet because its installation in ruby 1.8.x was always a tricky issue. Ruby needs the Onigurama regex library to parse the Textmate bundles. This means you have to install some software from a japanese geocities page and compile the onigurama gem. Ruby 1.9 uses this regex library by default, so Ultraviolet is a snap to setup.
Thanks to Heroku and RVM, it was pretty easy to get a ruby 1.9 app developed and deployed.