The official LinkedIn app for Windows Phone just hit Marketplace. Download it now
The free app lets you tap all the most popular features of the popular business social network. Search for jobs, see real-time updates from your connections, stay up-to-date with LinkedIn professional groups, and follow company and industry news.
LinkedIn also makes great use of Windows Phone-only features: Live Tile notifications let you know about new messages, invitations, and LinkedIn Today updates. You can also stay on top of selected professional groups by pinning them as a secondary Live Tile.
The LinkedIn blog has more on the app.