There is a pretty simple way, but there is a rather large flaw to it: all you have to do is go to the print settings in either Illustrator or InDesign CS, and go to Setup. Once there, there should be a option named "Tiling," and choose Tile Full Pages. The printer will then print the poster in a way which relies on the paper that you chose. You can move around the overlay in the preview given in the print settings menu.
The problem is, that unless you find a way to print flush (to the ends of each page), you'll always end up having a white border around each page, and when you compile the entire poster, it won't look as good as if you'd print it as one. If the poster is not that small, or if you are using tabloid sized paper, then you might be able to get away with it with little trouble.
Off the top of my end, an alternative is to specify a box dimension that is smaller than the given print page. For example, if I'm printing on letter size paper, which is 8.5in. x 11in. I would create a box in Illustrator or InDesign that is 7.5 x 10in which would act like a guide. Using boxes of this size, I would manually divide the entire poster into smaller sections, and print each section individually. After they are all printed, I would then cut the boxes out (so that the white space would be cropped), and paste them all together to form the poster, which would be almost seamless reconstruction.
Of course, if you want to save yourself some trouble, and want great quality, I would suggest going to a print shop. An example of prices is 19 x 30in. usually range from 30 - 50 CDN.