Who makes and owns your vote-counting software. Not just electronic voting machines -- optical scanners and tabulators as well. (They are, however, silent wrt the older Danaher machines used in Philadelphia, Franklin County, OH, and a few other places.)
As far as who can 0wn your vote-counting machines, well, read the book they have posted online.
Political donations received and given. For help in your purchasing decisions, you can search for company names -- look at Who Gives/Donor Lookup. As of this writing, not all 2004 data are present; suggest looking at 2002 and earlier.
