Currently our Law Frim pay 100% of the employee health insurance coverage, but dependent coverage is very expensive( over $500.00 for family coverage). How can I find information on what other companies are offering their employees? (ie, carriers, percentage paid by employer, etc.) How do I know if we are competive with other law firms and companies?

You could do a quick survey of other firms in your area. Most HR folks are always willing to help out where able. They may not give you specifics, but general idea's. It's a place to start. Plus you may want to try the IFEBP web site.