I wouldn't advise doing that unless you have some knowledge about VPNs and the ability to secure the network connection. In order to make the drive available over the network you'll have to set it up as a Windows file share. Then you will have to open up some ports in the firewall and enable address/port translation so you can get to it from the Internet. The main drawback is that once you can get to it, so can everyone else. You would need some means to control who has access. That's where the VPN comes in.
Linksys routers allow outbound VPNs, but very few can be configured for inbound. If you have a version of Windows server you could always set up RRAS. If you're Unix savvy, you could do it with Linux or one of the BSDs. But if you don't know what you're doing, you run the risk of having your PC get taken over as a spambot or worse.
It would be much more secure to just take the drive with you than to open up your firewall to everyone on the Internet.
