There are many free or cheap software programmes available on the internet for file integrity checking using the open-source MD5 checksum. Some that you may want to try are:
Fastsum - for Windows platforms
ImageIngester - for Windows or Mac
Exactfile - for Windows
Most versions of Linux have an MD5 checker, md5sum, included in their distro. You can find out more about the Ubuntu version here.
Two sources of free training and software to assist with preservation processes in your organisation are:
Digitisation of Heritage Materials - Free software training and downloads provided by the National Library of Australia
Digital Preservation Management tutorial - a free online tutorial on digital preservation management
Digital Preservation at the National Library of New Zealand - Sun Microsystems Case Study of the National Digital Heritage Archive, 2009
Preservation Information Booklets - National Preservation Office, National Library of New Zealand
Institutional Repositories in New Zealand: Comparing Institutional Strategies for Digital Preservation and Discovery -Brenda Chawner, Rowena Cullen, 2008
Care and Handling of CDs and DVDs - a Guide for Librarians and Archivists - Fred R Byers, National Institute of Standards and Technology, U.S.A.
UKOLN (UK Office for Library and Information Networking) - a resource centre jointly funded by MLA and JISC in the U.K.
Preservation Management of Digital Material Handbook - Digital Preservation Coalition Handbook
Preserving Access to Digital Information Resource Gateway - a preservation portal for international resources provided by the National Library of Australia
Digital Preservation: Managing Digital Collections - a page of resources about initiatives and innovative projects relating to Digital Preservation
Preservation Policy - OCLC Digital Archive Preservation Policy and Supporting Documentation, 2006
A Guide to Distributed Digital Preservation - Edited by Katherine Skinner and Matt Schultz, Educopia, 2010
Plenty of Room at the Bottom? Personal Digital Libraries and Collections - Neil Beagrie, D-Lib Magazine, 2005
Changing Trains in Wigan: Digital Preservation and the Future of Scholarship - Dr Seamus Ross, National Preservation Office, U.K., 2000
Public Sector Readiness for Digital Preservation - Dr. Daniel G. Dorner, Dr. Chern Li Liew and Mark Crookston, Victoria University of Wellington, 2006