Google has released a new cross-platform Firefox extension – Google Browser Sync. Basically it allows you to use one profile on multiple computers, with changes automatically synced up.
Netscape 4.x had roaming profile support. The relevant Bugzilla bug to reimplement it was bug 124029, which was fixed by Ben Bucksch back in 2004, with bug fixes up to late 2005. There’s even a Bugzilla component to track bugs in the implementation. I don’t know if the capability is built into FIrefox, or if it still works. As far as I can tell, it seems to be Seamonkey only.
The features and function look really cool – the only sad thing is that Google Sync is not free software. :-( So I can’t hack on it, or read the code to see if they are actually sending my “PIN” (the thing with numbers and letters that everyone else in the world calls a password, and which encrypts my stored information) to their servers, or set up my own server if I don’t trust them. So I’m not sure yet as to whether I’ll install it. Perhaps the release will inspire someone in the community to revive a free version.