Temporary phone numbers and eBay
When you are selling or buying something on the web, say eBay or Craigslist, it always is a question whether to give your 'real' phone number out. I just came across Numbr.com (credit Lifehacker, and several others) which appears to have a neat solution to this.
Simply, it gets you (for free, but doesn't everything have to be free nowadays?) a temporary phone number which will anonymously forward calls to your real number. Simple and useful. Check out Numbr.com.