There are several well-crafted websites on the topic of handicapped/disability travel, but one of the pioneers is the Access Able Travel Source which offers tours, resources and travel tales for the hearing- or sight-impaired and the physically handicapped, plus a newsletter and links to relevant sites. 

Families with disabled members will find the Society for the Advancement of Travel for The Handicapped site very useful, particularly the travel features from their magazine, Open World.  Other valuable online resources include www.GimpontheGo.com and www.emerginghorizons.com, homespun yet comprehensive websites managed by handicapped travelers, with their own publications.

Most major Visitor & Convention Bureaus publish special guides for the mobility, hearing or visually impaired: Toronto With Ease and the Virginia Travel Guide for Persons with Disabilities are two excellent ones. 

For cultural and adventure tours open to both the disabled and to children, explore the Specialty Travel Index magazine.

For a travel specialist who is knowledgeable about the accessibility features of resorts, cruise ships, and organized tours consult the ASTA site; and search their database of members by zip code.