There are a million ways to skin this cat, here are a few:
1) Use everything you already have
You can attach the drive to your Windows machine (formatted as NTFS) and share out the partitions as separate network folders. Your Mac will be able to mount that share using SMB. Directions are outlined here.
I use this very setup for doing exactly what you are attempting to do.
As far as the concern for reading/writing NTFS on Mac: You can download and install this free driver that will allow you to direct attach the storage on your Mac and read/write without any probs.
2) Use an AirportExtreme to share it out
Using an AirportExtreme and Bonjour, you can plug that puppy in and share it out across your network using Bonjour. Just plug it, fire up Bonjour and enjoy. In this instance, using HFS+ would be the best bet.
3) Do the inverse of #1
Format your drive in HFS+, share it out on your MacBook and enable Windows File Sharing. Use this article here for doing that:
#3 would be the least preferable since your MacBook is going to be on the run. #2 is the best in that regard because you get access regardless which machine you are using and doesn't require you to have both machines running. It is not as desirable since you would have to purchase additional equipment, so if you're looking reuse the equipment you already have, #1 would be your best shot.