Here are some, but I suggest you try looking for some addresses in google...
www.maxoncomputer.com/resources_browse.asp?catID=4 www.wiredchild.net/hdri/
Don't know about the software, haven't tried using HDRI maps yet, but as soon as I get into it I'll tell you...
There's good info on the subject in
www.rendermania.com/HDRI/
Good Luck!!