You can set up a GlusterFS cluster on your droplets. I believe the performance will be good enough as there is minimal latency between droplets (since they are routed in the datacenter itself).

If you want something simpler I've had sshfs work very well. (It's generally not fast enough to serve files from though, but give it a spin - if you cache a lot of things in memory it could work well.)

From what I have seen GlusterFS is just creating mirrors yes? I think what I want and what the original poster wants is to combine the storage of multiple droplets into one massive amount of disk space moutable on a main droplet. Can glusterfs do that? I am using SSHFS for now to just transfer files around my server but I would ideally like to have a big blob of space that is accessible locally.

@Morthawt: Yes, GlusterFS can do that.

I'm trying to think of a solution for this as well. I have several droplets and I would like to share *some* disk space between them, in a redundant way (I don't want one droplet going down to render some files inaccessible).
I'm used to do this in high-availability clusters with OCFS2 and a space on a SAN, with which (OCFS2) I've had great success (not so much with NFS v2). It is my understanding DRBD and GlusterFS are a little tricky to configure (they require exactly the same amount of blocks on each disk) and a little inefficient for large system (I read from GlusterFS that for anything serious you should have 8GB per machine).
Ideally, I would use one droplet as an OCFS2 "server", but I don't think I can do that (you need another type of connectivity to mount the disks on the hosts).
I'll try reading more about NFS3 for now, see if it brings anything better that would fix the caching issues I had with its previous version.

I would also like to know how we can best share files like a SAN on digitalocean.