.Mac, which already acts as an online repository for photos, movies and other files, has now been expanded to offer groups functionality to encourage online collaboration between users.
Subscribers can invite others to upload and share files, calendar and contact information; build e-mail lists; and allow and disallow membership using their .Mac site, the company said.
.Mac remains a subscription service. The cost starts at $99.95 per year.
Rob Schoeben, Apple's vice president of applications marketing, said the new features mean Mac users need not look outside of Apple for group communications. "Mac users shouldn't have to send an e-mail with an ad on the bottom, and they shouldn't have to set up their groups site on Yahoo."
He added that the company had examined an advertising-based model but decided to opt for a subscription model as it was more in keeping with the Apple tradition.
.Mac storage has also been bolstered to fit the new groups model. Individual users can now get 1GB instead of 250MB, while a family can use 2GB of combined storage, with options to buy more storage.
With the spruced-up .Mac, Apple users can access and synchronize all their usual Mac settings and files on any number of computers, including those running Windows.
"When you're away, you can still get a little bit of Mac, even on a PC," Schoeben said.
Jo Best of Silicon.com reported from London.