I have found the different websites to be really usefull in getting gigs. Myspace, Facebook and Mudcat have all helped. After going to a clubs singaround/session and later getting in touch via myspace when I get home because I am too much of a coward to ask for a gig there and then. I have even asked for gigs without meeting the organsers via myspace email, that so far has worked. I have had a few unprompted gigs to. So all in all I think Myspace is a really usefull tool to get work.
RE: Hiring fairs
I am not so sure about hiring fairs, I hear so many different reports about them, some good but most bad. Mainly that organisers dont go and you are really just playing to other musicians. But in a business where you need to make a name for yourself when you are new to it (like me) I dont think it does any harm to do them.
I would love to do a few and give them a go but by the time I find out about them they are fully booked and usually by the same people performing.