Legality of adding music?

Hi everyone:

Like a lot of other people, I'm not new to blogging or producing video –
but I'm new to videoblogging. I have a question regarding music clips in
videoblogs. Is it covered under Fair Use? Is it illegal? I include music
in my own personal home movies, but I've never distributed content like
this over the web — so I'd like to hear your thoughts. Thanks,