NARIC collects more than 2,000 new documents every year.  Included in there are more than 1000 articles, books, and reports on the ADA:

http://www.naric.com/research/rehab/results.cfm?search=2&type=advanced&all=&exact=americans%20with%20disabilities%20act&any=&omit=&fld1=Title&txt1=&op1=AND&fld2=Title&txt2=&op2=AND&fld3=Title&txt3=&op3=AND&fld4=Title&txt4=&dte1=&dte2=&available=0&online=0

or try this tiny one:

http://tinyurl.com/ADAdocs