I need to keep two things syncronised: one on a weekly basis, the other almost always.
the first is my iTunes music folder, where I buy new songs every week. currently, what I do is purchase them on my B&W, sync my iPod, unplug it, plug it into my pismo, fire up iTunes, and click "sync purchases from iPod" from the file menu. This is OK, but it's not perfect for 2 reasons:
1. it only does purchased music, and not other songs I may have added on either machine
2. it is an extra few steps I would like to cut out.
so, essentailly, i need something that can sync these two on the fiy, automatically, every week, and move songs from one to the other, and vise versa, with little to no interaction.
the second is my gmail account, which I access through Mail on both machines. What I am looking for is something that can do like what my .Mac account does: where it has the messages in my inbox the same on both machines, with their read/unread status intact.
again, little to no interaction. Prefferably freeware in both cases, if it involves a new app.
-digital 
What you want sure sounds nice. But doesnt exist as far as I know.
Here are my two suggestions:
I dont use the gmail account from anything but the web, it sounds like it would be smarter to go back to using that solution, since it essentially mimics an "IMAP" folder. I use the mac gmail notifier, have it on my work and home computers and it makes it pretty much work like what you are looking for. Are you pulling the gmail email in a POP setting? Sounds like it. If you are, can you instead use IMAP or have one of the accounts use the "leave a copy of the email on the server" setting?
the second one is a bit trickier. Since what you are trying to do is not sanctioned by Apple, since only one ipod is "married" to one iTunes account. However, when I get into that situation you described, I use Senuti (itunes backwards) it allows you access to all the music on your ipod. Simple interface, free. Scripting it or automating it is a bit beyond what i can offer.
http://www.fadingred.org/senuti/
dvsjr
yeah, it's pulling the gmail account over POP in Mail on both computers. I am not familer with IMAP. Does gmail support it? I think Mail does, as I was reading about it.
also, I think I figured out the itunes thing, though it's not eligant. Both computers are tied to the same .Mac (and therefore iTunes) account, and iTunes allows up to 5 machines using the same account. What I did is purchased my songs, synced my iPod, unplugged it from the B&W, and plugged it into the pismo. Immidatly upon launching iTunes, I got a message saying that some of my purchaces on my iPod were not in my music library, and if I wanted to add them. I said yes. there is also an option to do it manually under the file menu in iTunes ("sync purchases from ipod" or something like that). It's not eligant, but it works.
edit: forgot to mention I downloaded google notifier on the pismo. quite nice, and i'm going to dl it on the B&W. menubar is looking a bit crowded on my pismo with spotlight, fast user switching icon, time dd:hh:mm:ss, input menu, battery, volume, sync, iChat, classic, airport, coconutwifi, show desktop, and google notifier. On 1024x768, that's no fun.
-digital