Have you scanned bound books, only to find that the pages are curled near the center binding? You also may have noticed that some of the pages are skewed. A program called "unpaper" may solve those problems. Please note that the software only runs on Linux systems. I haven't yet used unpaper but it looks promising.
Quoting from the unpaper web site:
unpaper is a post-processing tool for scanned sheets of paper, especially for book pages that have been scanned from previously created photocopies. The main purpose is to make scanned book pages better readable on screen after conversion to PDF. Additionally, unpaper might be useful to enhance the quality of scanned pages before performing optical character recognition (OCR). unpaper tries to clean scanned images by removing dark edges that appeared through scanning or copying on areas outside the actual page content (e.g. dark areas between the left-hand-side and the right-hand-side of a double- sided book-page scan). The program also tries to detect disaligned centering and rotation of pages and will automatically straighten each page by rotating it to the correct angle. This process is called "deskewing".
This sounds interesting but I will caution that unpaper is not for computer novices. It only runs on Linux and uses the command-line interface. However, if you are familiar with Linux's syntax, you might want to check out unpaper at http://unpaper.berlios.de.