When the Web isn’t sucking away your time with utter silliness, it could be helping you brush up your musical chops. Here’s a roundup of useful resources, all of them completely free, for a variety of skill levels, whether you’re trying to learn to play with half-diminished chords or build yourself a DIY drum trigger for controlling software. And I’d love to assemble more of these if you’ve got some tips.

Drums: There’s an enormous drum lessons database at DrumBum.com, with everything from cymbal cleaning to dumbek. And of course, we’re especially interested in the DIY drum triggers how-to. This isn’t just Web community-contributed stuff, either; you’ll find drum celebs like multi-Grammy artist Paul Wertico. (More on him later this week.) And for a little inspiration, check out the section of drum solo video clips, like the one of Keith Carlock of Sting and Steely Dan fame, pictured below. (via AudioMastermind)

Guitar: iCompositions.com, the GarageBand-focused music community site, this week unveiled a set of free guitar lessons from member Ed Nicholson. There are four QuickTime movies so far on scales and chords, with more planned. A free registration is required for viewing. While you’re there, you can also check out some free GarageBand tutorials.

Keyboard: I regularly write for Keyboard Magazine, but like many of you, I rarely sit down with the keyboard chops lessons included with the magazine. Very often, something isn’t of interest to my playing, or I just don’t have the time. (Sound familiar?) Now, though, you can quickly navigate to what you need, because the entire Play section is online, grouped by skill level. The guys who contribute to this section are some mean, talented keyboardists, so it’s worth checking out what they have to say — and maybe picking up something fun to add to your practice routine. MP3s and printable GIFs of the sheet music (pictured above) are all there. I think I can safely share this one despite the conflict off interest, because I’m going to go have a look.

Theory: It’s not new, but it’s been making it’s way around the blogosphere: Ricci Adams’ Musictheory.net is an invaluable collection of Flash-based lessons, trainers for drilling instrumental skills and ear training, and utilities like blank staff paper printers and chord calculators. The collection has been growing rapidly, with a lot of new, useful stuff; early versions were pretty basic but he’s working his way into more advanced theory (read: the stuff you could probably use freshening up). I’ve used these in theory courses with students, and they’re pretty handy, at least as a supplement to resources on paper. You can also download the archive so you don’t have to be online to use them.

Got some other online resources you’ve found useful? Hit comments and let us know.