Sacramento Sky Ranch, which sells airplane parts, has an RSS 2.0 feed dedicated to light aircraft maintenance, including pictures and even sound.
There’s lots of great stuff here, from the sound a cracked cylinder makes when you flick the fin (yes, there’s a WAV file!) to why an oil/air separator to an engine is (in their opinion) an incredibly stupid idea. It’s aimed mainly at mechanics, but there’s good information for the owner/pilot as well. I’ve subscribed.