There is definatly software out there that does this.
I've got a Western Digital External Hard Drive (Passport type).
It came with sycronisation software that allows easy syncronisation of my files. But it has an added function of syncronising Outlook data.
I can sync. my Outlook files onto the drive, unplug it and take it away with me. Later I can plug it via USB onto another computer running Windows (XP or newer I think) and I can view the emails. Better than that though, it can operate as it's own client...I can download emails direct to the hard drive by connecting to this other computer (no need to have Outlook installed on this other computer) and similarly it has a secure web browser onboard to, so I can do the same with my favourites.
The only thing it doesn't resolve is if you connect via a network that prevents access the mail ports.
When I get home I can then sync. my emails across to my own computer.