The main U.S. law concerning disabilities is the "Americans With
Disabilities Act." The Act is codified at 42 USC 12101 et seq. (see "United
States Code").
The Department of Labor has an ADA Information line (1-800-514-0301).
Also the Disabilities and Business Technical Assistance Center's library
will provide information (1-800-949-4232).
The Americans with Disabilities Center posts the Act, plus related
regulations and documents.
Westlaw has the Individuals With Disabilities Education Law Report in its IDELR database. The Department of Justice posts ADA regulations and DOJ enforcement and settlements. The Social Security Administration posts information on disability
benefits.
Treatises: Good legal treatises discussing disabilities law include Employment Law Guide to The Americans with Disabilities Act,
the multi-volume Disabilities Law Reporter and CCHs Accommodating Disabilities.