Alright, here's my situation. I'm getting a laptop soon, and it's going to be dualbooted with either linux/vista or linux/xp (probably the former). I haven't used any form of full disk encryption before, so I'm rather new at this. Anyway, I'm not entirely sure of all the details yet, but most likely the partitioning will look something like this: Linux (ext2), Data (ext2), Windows (NTFS). All my important stuff (e.g. movies, music, work-related stuff) will be on the data partition, encryption of that is most critical, though I want the other partitions encrypted as well.

What I want is a way to more or less transparently access the linux and data partitions while in linux, and access the windows and data partitions while in windows (I'm aware I'll need to install windows support for ext2). I'd want access of the data partition to be quick/convenient from linux moreso than windows, since linux will be my primary OS. I'm rather undecided on the implementation of this. Any help/suggestions would be appreciated.

You're more than likely going to need different encryption technologies in the two OS's. You should make your shared data partition ntfs and install ntfs-3g in Linux to read/write to it. Vista has it's own encryption technology called "bit defender" which is available with Vista Ultimate and Business editions I believe, I'm sure you can implement it in a lower end version of Vista also. Will Linux be able to access the data partition is another question. I don't think you'll find encryption software that will allow the two to access each other's file systems, that's the whole idea behind encryption, "security".