1. The Coworking Visa.
The coworking visa is one of the greatest largely-unknown sources of added value to participating coworking spaces, and also one of the most impressive examples of value-added cooperation across competing businesses I know of in any industry. If you're a member of Locus or of another coworking space that participates in the visa program, you may know about it already. This is an informal group of about 500 coworking spaces around the world that have agreed to let members of other "Visa"-participant coworking spaces use their space for free (usually for up to 3 days, but the terms depend on the space; Locus is free for up to a month, but limited by the terms of the other coworking space). Here's a link for details with the list of participating spaces and their terms, organized geographically.
The coworking visa was the fortunate brain-child of two of the women leaders of the coworking movement, Julie Duryea of Souk in Portland, Oregon (now run by someone else and maybe under a different name) and Susan Evans of Office Nomads in Seattle, Washington. They proposed it on a google group to a network of people running coworking spaces around the world, and it was almost immediately successful.
2. The Prague Coworking Visa.
A group of coworking spaces in Prague (including Locus) were inspired by this visa program to create a Prague version of the visa that allows members of each space to use the other spaces for up to 25% of their membership time. See details here.
Loosecubes is a corporate alternative to the Coworking Visa and it remains to be seen whether their intentions are pure and how well the system will work, but as it stands it looks very promising. It is an invite-only workspace-sharing network of about a thousand coworking spaces and other shared offices around the world. Right now (and from what they've told me, this is their permanent business model), their system is absolutely free for members of the network (including Locus Workspace members). This means you can use any of the other spaces on the Loosecubes network for free, though each space has its terms in terms of number of free days. So if you're traveling abroad and want to cowork in most major cities around the world (though biased towards Western Europe and North America), you'll have a coworking space to work at for free. Loosecubes also provides a software backend and a user-interface that make it easy to use and (it seems at least) perhaps more reliable than the Coworking Visa.
Jelly is informal coworking that started around the same time as the coworking movement itself with a group of freelancers in New York City who decided they'd rather work alongside other people than alone in their home office or at a cafe. They starting meeting as a group at each other's homes or cafes, they created a wiki, and Jelly grew into a movement, with groups meeting to work together rather than alone around the world. Here's a sample list of Jellies around the world on Meetup.com.
The group of collaborating coworking spaces in Prague mentioned earlier hosts a rotating series of jellies across their three spaces, which means people who don't work in a coworking space (and may not want to) can experience some of the benefits of coworking for free every two weeks, and get to know a few of the coworking spaces in the city in the process.
To me the added value that comes from sharing membership across coworking spaces (and with the public)--not just for independent workers and coworking space members, but also for the coworking spaces themselves--is immense. For the members, of course, it means they can literally work their way around the world (as long as they stick to major cities), for the price of the coworking space membership they already have at their home city. For coworking space owners, it means a wonderful influx of interesting visitors who add spice to the host spaces and use resources that were mostly available and going unused anyway!