Wetpaint.com
Sure, your pals can post comments about your blog, YouTube videos and Flickr photos, but if you want a true collaborative exchange, consider creating a wiki—a site where anyone can add and edit any of the site's content. Wetpaint, a Seattle startup, makes it super easy for non-techie people to create a wiki or contribute to one. Even companies are using it: Food & Wine magazine has a Wetpaint wiki; CBS started one for CSI fans and T-Mobile created one for the Sidekick.
The process for adding text, Web links, photos and video to a Wetpaint wiki is highly intuitive, but there are video tutorials just in case. If you're feeling protective or want a little more control, Wetpaint lets you set different levels of access for different users. You can also restrict access altogether to only those you've specifically invited, though anybody will still be able to visit the site. As your wiki evolves and grows, there are tools that track the changes in detail, so you can see who did what and when—and then call them on it before changing it back.