Do you know about ctrl+cmd+t, click on magnifying glass and use Key equivalent -- with this you will get to know if there is a binding for your wished shortcut in the bundles.
For the rest it would be just useful if there would be some kind of a cheatsheet (if this does not already exist).
You can generate a comprehensive cheatsheet with ⌃⌥⌘K (Textmate > Show Keyboard Shortcuts). This doesn't restrict to just the current scope though… I guess that's what ⌃⌘T is for.