TweetMyJobs is a free Twitter-based job-board service that provides instant notification of open positions. Actually, it's free for job seekers; if you want to offer a position, it'll cost you a whopping 99 cents. That's for a one-day posting; the 30-day option costs $9.99, or you can do 3 days or 7 days for $1.99 and $4.99.
If you're in the seeker category, just sign up for a Twitter account (if you don't already have one), then subscribe to one or more TweetMyJobs "job channels," of which there are nearly 5,000. Just specify your city and state, then choose your industry.
When the service finds a match, it'll tweet you. And assuming you have Twitter configured accordingly, those tweets will arrive on your phone via text message. How awesome is that? It's like having your own personal headhunter.
Ah, yes, another practical business use for Twitter. And while we're on the subject of jobs, be sure to check out Great Resources for Finding Work Online, Need a Job? Turn Social Networks Into Job Networks, and Find 'Hidden' Job Postings at LinkUp.