I often scan in music from bulky books. I find Scan Tailor (http://scantailor.org/) works pretty well. It lets you crop, unbend, despeckle etc. in a wizard like way. The drawback is that it wierdly insists on TIFF format input and output. So you have to be handy with tools like pdf2pnm, pnmtotiff, tiffcp and tiff2pdf, etc.
Works really well apart from that.