One of the great things about TextMate is it’s extensibility.
The developers built in this ability to add more blades to the Swiss Army Text Editor through what they call Bundles. I haven’t looked at how to create custom bundles, but you can easily enable/disable them to suit your needs. Bundles allow TextMate to do things that I used to need individual applications to accomplish, like using Ecto to have a full-blown, offline-capable blogging client.