At work I frequently switch between quite a few computers: two Macs, one Linux box, one Windows machine, and the occasional Chromebook. Between a KVM (for the desktops) and a swiveling chair (for the laptops), this isn't so bad. The one part that felt awkward was the lack of unified clipboard support, which would be handy when IM-ing links or checking out URLs on multiple computers.
I initially used Syncopy to solve this problem, but it didn't fully solve my problem (due to being Mac-only). Additionally, I didn't really like the idea of my clipboard contents ending up on the developer's server (or having to run a local, could-be-doing-anything binary). Eventually, Syncopy stopped being a viable solution altogether since the developer abandoned it (see the reviews for the iPhone client).
It occurred to me that I could build a replacement as a Chrome extension. Extensions can access the clipboard, and the storage API provides a synced key-value store. Some quick experimentation showed that changes were synced within a few seconds, which was good enough for my needs. There was some rate-limitting, but it didn't seem like it would affect any day-to-day use.
Clipboard Sync (source) is my implementation of that idea. Its main UI surface is a browser action icon. When you want your clipboard synced, click the icon. On all the other Chrome instances that are running and are synced with the same account, you'll get a notification saying that the clipboard data has been pushed. Click on the notification, and the local clipboard will be updated (and the notifications on the other instances will be dismissed).
Clipboard syncing was actually filed as a feature request for Chrome a couple of years ago. It was (rightfully)
WontFix-ed since it's a pretty niche feature. It's quite reassuring that the extension system is now flexible enough to allow it to be implemented pretty seamlessly (especially once the commands API hits the stable channel).