Wow. Synergy + Marco Polo = Lots of automatic goodness.
I've got a laptop and a home computer which occasionally cross paths. When I bring the laptop home, I like to use both it and my home computer in parallel -- sometimes compiling/linking software on one, while doing research on the other. Synergy works great for sharing my keyboard/mouse between them. Now, with Marco Polo though, life just got even lazier!
Rather than manually starting the synergy daemons on both machines, Marco Polo let me set up some network 'evidence' policies (available wifi ssid + bonjour services) which detect when my computers are at home, near each other, or at work and execute various 'actions' based on that 'evidence'. Some of the 'actions' I have set up thus far are :
[Both machines] Automatically launch the synergy daemons (on both machines) to share my desk's keyboard/mouse when laptop & desktop are both at home
[laptop] Launch my work chat client (iChat) at work, and my home chat (Adium) client at home.
[laptop] Set my iChat status to 'at work' when at work.
[laptop] Set the default printer appropriately based on location.