How refreshing to stumble into a trade show that has its eyes on users and their collaboration. Enterprise 2.0 came to San Francisco early this month, and I liked what I saw.

Take, for example, Liquid Planner, the hosted project manager. Unlike conventional planners, it makes no demand for the single completion date, so laughable in practice. This planner avoids roulette thinking by asking instead for a range of dates — much easier to believe in.

“One of the biggest problems in business is keeping people engaged,” says Liquid Planner CEO Charles Seybold. “If they’re not engaged, they go away.” They disown data they’re supposed to engage with, and that accelerates their drift away from corporate goals.

The planner also makes use of collaboration in email, Twitter, and other media to measure progress, obstacles, and project creep. Did you and a bunch of coworkers sketch a revised timeline on a paper napkin at lunch? Even that could be scanned and added to the mix.

“It’s all about people working together,” says Seybold. “It’s all social” — an obvious but usually ignored fact about business.

Other vendors make more general use of social media. SocialText, for example, picks up on social media to give overall business collaboration a push. It’s already got about 5,000 customers around the world, according to the man at the SocialText booth who rattled off the features: an iGoogle-like dashboard, secure and selective access, open standards, and so on. The pricing looked engaging, too: free for operations with fewer than 50 users, then $5 per user per month.

Away from the exhibition, 116 attendees packed a room to hear Linden Labs announce a business version of its virtual world Second Life, Second Life Enterprise.

Remember when people were impressed with a computer singing “Daisy, Daisy, give me your answer do”? The virtual meeting Linden Labs used in the announcement will someday be compared to TV productions of the early ’50s. Eventually, Second Life Enterprise will work out the kinks and start to walk, run, sing, and dance. As I wrote in May, someday we’ll see serious what-if scenario gaming.

This is the future of intelligent business.