Since I upgraded from a single laptop to dynamic duo including a new desktop, the "how do I keep the two in sync" problem became a topic of some significance on my geek life.
There are several sets of information that I want to keep in sync, and for some of them I found solutions, and for others I'm still struggling.
The first and easiest to solve was my
work/ directory. This directory has all my code, in subversion checkouts or git repositories. The solution was a single Unison profile that I manually have to run at the begging and end of the day. It's not an automatic process and it is not transparent, but sometimes, and in this case, I see that as a feature. I also include my dotfiles in this work directory, so all Macs share the same set of UNIX-style configuration files.
Then we have "other files". This is a category for random files, documents, PDF downloads of stuff to read, whatever. This is also perfectly solved by Dropbox. I could not in a million years write a better explanation why Dropbox is great than Michael Lopp's article Dumbing Down the Cloud, so read that and you'll understand why it is really really great. (Update: but make sure you understand some of the limitations with as pointed by Michael Tsai).
One important part of my day is my personal R&D time, about 1 hour per day where I read a lot. I find stuff to read using RSS feeds, about 350 right now, that are kept in sync using NetNewsWire and NewsGator service. It is not nowhere near perfect, the snippets system easily gets out-of-sync (16, 66, 12: that's the number of snippets I have on the web interface, desktop NNW and laptop NNW right now...), sometimes I get an old feed back from the dead, all marked as unread, and (most infuriating) the order of the groups is not synchronized between instances. But it "works" well enough. I'm considering the Google Reader as an alternative, but I admit that I would prefer to keep using a desktop application.
After these three, I still need to tackle my mail (and more important, my mail configurations), my address book, music, photos and applications.
The last three I just don't bother. Applications will be re-installed on each computer without any sort of sync between them. I just install them when I need them. Music and photos are not synced, at all. I could use the desktop as the master and just
rsync them from time to time to the laptop, but it wasn't worth it yet. Eventually I'll get a new iPod (all my iPods are currently dead), and I'll use that when I'm away from the desktop.
But the other two are still unsolved. Although all my mail is stored on IMAP accounts, I have a large set of local rules that are not easy to synchronize. I know about MobileMe (not worth the cost, and the "went wrong" stories scare me a bit, even with decent backups) but I'm still looking for some other alternative.
One possible solution that I'm considering is a change in my workflow: make sure all my rules only apply to a "To Process" mailbox. When scanning through the inbox, I either reply/forward, delete, or move the that special folder. Then, on the desktop, I just run all the rules and the messages are archived properly. This would allow me to keep the rules in a single computer and still read mail on all of them.
The same for Address Book. Although only a single file needs to be kept in sync, and given that MobileMe is not an option for now, its still unsolved.
I bought the newest Take Control of Syncing Data in Leopard, in the hope that I can solve the last to items on my checklist. Time will tell, I guess.