UPDATE: First 8 comments get an invite!
Ed. Note: Apologies for the down time! I’ve been immensely busy between travelling, setting up a home office, and working on a startup. Hope things can get back to normal from here.
Mento, founded by Greg Hochmuth, is a new service based out of Germany and that entered private beta very recently. The service is based around the idea of sharing links with the people you care about. It’s not quite Digg, it’s not quite Tumblr, and it’s not quite Mahalo, but a weird mix of all three with a bit of its own.
The service is a easy signup — one of the more intuitive processes I’ve seen recently. At the end of it, Mento gives you a handy “Share with Mento” bookmarklet, which is a main input mechanism into the service. Whenever you’re visiting a link, pressing the bookmarklet reveals a bunch of actions that can be taken with the link. This also defines Mento pretty well in general — you can send the link (supplying a friend’s name/linked with Facebook, an e-mail, or a group/tag), save/bookmark it del.icio.us-style with a description and tags, or add a reply to a recently-bookmarked link on the site in your network.
While the input/sharing mechanism is one main aspect of the service, it’s not the only one. Going to to the site’s homepage, mento.info, reveals the “receiving” end of the spectrum. Among this is your own “Mento 
Mix” which shows the links shared by your friends and network recently, an “Inbox” which shows the links and replies sent specifically to you, and a way to customize your Mento Mix which is a way to tell Mento the kind of stuff you like to see and don’t like to see.
Additionally, the “Your Links” tab on the top shows your own recently shared links, “Your Network” allows you to manage your contact list and add/invite new friends, and “Channels” lets you join specific groups and categories of like-minded people with similar interests who collect and share links together. This aspect of the site is very much like a YouTube for links where the focus is on aggregation the whole community’s shared items as opposed to the links shared to you by your friends (which is the site’s main purpose).
A really cool thing about the site is being able to link and work with other services. For example, you can connect your Facebook account so that linked shared with Mento 
are automatically shared with Facebook as well. Additionally, you can export your links to FriendFeed, Twitter, Magnolia, Tumblr, or Del.icio.us all at once, and even use Twitter as a e-mail/bacn replacement to get notified about replies and recommendations.
Aesthetically and simply in the way it works, Mento is a solid product. There has been thought put into its design and interface and the way it looks, feels, and works very much serves to its purpose of building a community around link sharing. Being a heavy Tumblr, Del.cio.us, Twitter and FriendFeed user, I still have to try its integration points, but if it works the way it’s supposed to, I might as well use it as my primary bookmarklet to share something interesting on the web as opposed to twittering, tumbling, and del.icio.us’ing one link three times.
And as the site itself gets built outward and collects more users/my friends, I think I could find a use for it myself in discovering and sharing links. Personally, I think the service is on its way to being a success among other services like Twitter, Del.icio.us, and Tumblr in the area of link sharing if it’s able to somehow gain a good tipping point. But don’t forget, I called it first. 
