Uploading Big Maps

I made a map for my campaign, and the file size is 34mb, which I obviously can't upload to my library.  Any particular way I can cut this map up into several parts to upload while still maintaining grid alignment?

Well, to begin with, I'd try and reduce the size of the map. Even cut up into sections, it is likely to cause issues. Make sure it is jpg, not png, and saved with as much compression as you feel you can get away with. Also, keep the resolution low. Most maps are produced at either 70 or 140 pixels per unit. Make sure you aren't oversampled. That being said, the actual technique will depend on what your graphics program is. In Photoshop or Illustrator, creating slices is trivial. Some other programs may require more manual intervention.