One interesting project is Syncthing, that I use across my devices. So far, the only problem is memory -- in my workload it uses about 60-80 MB, which makes it problematic to use on my NAS and e-book reader (both having 32MB RAM). Still, work and home desktops, two laptops, N9, Palm Pre2 and Android tablet (Yoga 1) enjoy synchronization without any "cloud" storage (although external discovery and relay servers may be needed to circumvent NATs, one can run own instances).

By the way, how can I persuade upstart to run syncthing daemon for me? For now I just start it manually after reboot, which thankfully happens rarely enough...