There should be a .dbf file (holds the attribute data) and a .shx file (links the spatial file .shp to the attribute file) to go along with the .shp file. There may be others as well, such as .prj to hold the projection information, and perhaps .sbn and .sbx to hold index information.
If all you want to do is view the attribute information, the .dbf portion of the Shapefile is just a dBase III format file, so anything that can open a dBase III or newer format should work here.
ESRI Shapefile format is published as a whitepaper.
http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf
As another poster already suggested, ESRI has a free viewer. It is a very popular format, so almost any GIS engine will allow you to view it and several allow you to edit data in that format, including several open source ones. If you want an open source viewer/editor, check out the this site which lists lots of them
http://opensourcegis.org/
Of the software listed on that site, I have used the GISToolkit and know it will allow the viewing and editing of Shapefiles, but perhaps there are others that do it better.