This sounds like one of those 'email or e-mail' questions. I for one prefer online learning or just learning; interactive or web based learning are OK too. However it may not be online and it may not be interactive, but it could still be computer based. Think most people agree that CBT or computer based training is terrible and is evocative of those CDs containing lots of worthy content which no one ever watched.

I don't know if there is a definitive answer - write in if you think there is. Word 2007 UK English spelling accepts e-learning and thinks elearning is a spelling mistake. Google gives 12,100,000 results for elearning and 46,400,000 results for e-learning, so I think at the moment e-learning is the way to go.