I've been animating for 5 years now and I mostly learned from whatever online sources and video tutorials I could find (I'll post some useful sites at the bottom). However the thing that really got me to the next level is this video training series which I highly recommend you check out if you're serious about learning animation:
It's $100 but it's completely worth it, trust me.
It teaches you all about acting and storytelling, as well as the entire animation process from blocking to polishing. You can check out the first episode on poses here:
Also check out The Animator's Survival Kit. The DVD's are kind of pricey, but there's also a book. Here's a really cool clip from one of the DVD's about timing and spacing:
Here's some Blender sites to check out: