Just use the DOS format. Contrary to popular myth, Mac apps and files hold up fine on DOS formatted disks. Just don't mess with or delete any invisable Mac files, that may show up on the PC, which may destroy Mac resourse forks or directory structures.
I've personally never had a problem with Mac files on DOS formatted disks, all of my external Firewire HDs/Media cards, etc are DOS format, and I use them back and fourth between my Macs and PCs no problem.
I'm not sure if it's possible to have disk partitions in completely different formats,never tried to do so. Would be interesting if that works.
If using a DOS formatted partition with a Mac is too foreign for your tastes, get something like MacOpener for the PC and use Mac formatting.