Member counts - find out how many certified SLPs or audiologists are in your state; has general breakdown of where members are working to give you a sense of how many of that state number may work in your setting
Member directory - use to find other members in your city who are providing services in a similar setting as you
ASHA ProFind -use to find others who are listed as working with the same age range as you intend to work- not an exhaustive list
Other resources to identify competition
Local phone listings
Internet search of practices in your area
Attend local small business meetings and network to find out who else in working in your area
Attend state or local speech and hearing association meetings; join the private practice section if one exists