Most of the U.S. inland waterway charts are available for free from
the U.S. Army Corps of Engineers:

You can download charts graphically from
http://crunch.tec.army.mil/ChartServer/jsp/index.jsp

These free charts can be viewed using the free viewer:
http://www.fugawi.com/viewenc/viewenc.html

A full GPS navigation software package, FUGAWI Marine ENC is
available, which supports these charts for $198, see
http://www.fugawi.com/docs/navframe.html


-John