I love how Blackboard, despite years of legal intimidation and generally anti-competitive practices, is slowly being picked away at by the competition, not from some monolithic replacement but by smaller, targeted services that do one thing really well. Tabule looks very interesting. Two of my classes this semester are using Piazza for online discussions. What Piazza does to stop spammy emails is let you set a digest to aggregate all messages every n hours, which I really like.
Yeah, I've also been working on a startup in this space -Notable ( http://notable.ac ) - It allows students to take their notes collaboratively online, and everything is linked to the page in the course slides that it relates to. You can also ask questions on these documents and have them answered inline.
My school has recently switched from a branded variant of Blackboard, to Desire2Learn which bills itself as open, etc. From a student perspective, the usability is not much different.
One "feature" that drives me insane is it creates zips on the server side every time you download a file (e.g., lecture slides, PDFs) even if the download is only one file. Effectively blocks one from using it on an iPad.
