Often, I find issues with the internals of Ubuntu and I don't know how to effectively assign the bug to the right project/audience.
Take this bug for example, regarding multiple monitor support. I'd like to file this bug against Gnome, but I don't know which of the many Gnome projects apply here (or is it actually a problem with X? or gtk?). I can't even search for gnome-related projects or packages, as Launchpad complains:
Too many matches. Please try to narrow your search.
I've tried asking on #ubuntu and #ubuntu+1 but received no help due to the very high amount of ongoing activity: IRC just doesn't scale.
As a result I had to mark the bug generically against Ubuntu and now it's just one of a dozen emails that the poor souls subscribed to the project receive on a hourly basis. I doubt the bug will get any attention this way.
How can I effectively target a bug with non-frontend components of Ubuntu? Where can I get help with targeting such bugs?
This guide should help you narrow down the right package. For bug triaging help find someone in the Bug Squad or ask on their mailing list or in #ubuntu-bugs.
The bugsquad has regular meetings and can probably find you a mentor if you want to help (and join!). For reference here's the Bug Triaging Guide.