Is there a free and easy program I can use to reduce the barrel distortion in the photographies ?
check out following thread on Flickr, there are a couple of other photo editing apps that can help, http://www.flickr.com/groups/gimpusers/discuss/72157613027928462/
Well he best will be photoshop, but is a little expensive
Panorama Tools is freeware and has distortion correction tools. It is a Photoshop Plug-in, but it will probably work with most image editors that take plug-ins. Even Irfanview takes most Photoshop plug-ins