LinkedIn is now the second-largest social network in the United States, finally surpassing Myspace with nearly 34 million unique visitors. Alongside this success, Roger Lee has created an unofficial addition to LinkedIn called Job Change Notifier. According to TechCrunch, the service uses LinkedIn’s API to let you know when any of your LinkedIn contacts update their jobs on the site.

Groupon.com has raised $135 million from Digital Sky Technologies and Battery Ventures, giving the company a $1 billion valuation. Groupon is profitable and has 270 employees. Groupon launched only about a year ago and previously raised about $5.8 million from New Enterprise Associates and other angel investors. Groupon e-mails a daily deal to people across major cities that offers huge discounts for services, assuming that a bulk number of people sign up for it at the same time. If the required number of people do not sign up, nobody gets the deal or discount.