There are a number of great agencies, firms and organizations that can assist vendors with improving the compliance of their products. A number of them also provide service training and free webinars to inform designers and developers of technology advancements and tricks to making products accessible and usable. To name a few:

Testing Tools

Automated tools can catch a number of compliance issues, however, some will need manual checking.

Depending on your product, there are some great testing tools to assist you along the way. 

Interesting ones that have come down the pipeline recently include:

Some enterprise testing tools include: