Less than 18 months ago, LinkedIn was the only online business networking game in town. Then Facebook opened up to all comers, and things changed. Or more precisely, a wave of LinkedIn’s users began giving the fast-growing social network a whirl. Sure, Facebook was more about throwing chicken wings than getting a deal done, but some of the hardest charging dealmakers, including startup entrepreneurs, venture capitalists and sales pros began setting up camp at Mark Zuckerberg’s happy online party.

Say what you want about those annoying zombies (a Facebook widget that lets you turn your friends into zombies with a digital “bite”), but LinkedIn looked downright dowdy by comparison. And worse, as more professional types signed up for Facebook over the past year, it became clear that LinkedIn didn’t have a lock on being a no-nonsense business utility.

Now LinkedIn, which claims 17 million members, aims to bring all those wayward people — and then some —  back. Starting today, LinkedIn is rolling out a set of features that aim to make your LinkedIn network as appealing and sticky as any other social network out there, zombies be damned. (See my CNNMoney.com colleague Paul LaMonica’s take on the new LinkedIn here.)

The LinkedIn update includes a refresh of the service’s homepage and the addition of modules that make it easier find people to add to your network, review positions your colleagues are looking to fill, as well as see the questions your LinkedIn network is posing to the community.

The revamped site also features the launch of LinkedIn News, a set of headlines gathered from thousands of sites and blogs that are meant to be tailored to you specific company, industry and the people within your network. For example, when I log into LinkedIn now, the news it gathers up for me includes four stories related to the relaunch of Fortune.com and the latest highlights from the magazine. The LinkedIn News feature will be rolled out gradually to all members in early 2008.

What promises to bring the greatest changes to LinkedIn, however, is the announcement of “InApps,” the service’s version of a platform to allow hand-picked third party developers to add applications to LinkedIn that will operate within LinkedIn but also bring your LinkedIn network and some of its functionality to outside websites. For example, BusinessWeek.com has developed an application via InApps that links to people and companies in your network that are featured in a story. LinkedIn is also a member of Google’s OpenSocial, but that is a separate effort.

The other applications to come are yet to be revealed, but LinkedIn brass is making it clear that those widgets that will be strictly business. They seem to mean it. Jia Chen, founder of one of the most successful widget companies on the planet, RockYou (which brought the social networking world such apps as GlitterText, ShoutOuts and Facebook’s SuperWall) says he e-mailed LinkedIn’s founder Reid Hoffman to see if they could get on the “white list” of approved developers. “So far, I haven’t heard back,” Chen says. “But you’ll see us on LinkedIn some day.”

Let’s hope so. While LinkedIn positions itself as “a purpose-driven site, not a happy waste of time,” it would do well to supply its members with a little bit of fun and, dare we say “glitter.” Without it, the site runs the risk of becoming too much like, how to put this, work.