Almost anything you can and want to do can help the cats!
There are many ways to volunteer and no job is too small. General descriptions of the more common volunteer positions noted below are either with an existing group or organization or may be an individual endeavor.

A number of them require training and a certain time commitment. Training requirements can be waived based upon previous experience. When necessary, the CRC will provide training at no cost.

Primary Volunteer Opportunities
Colony Management:
-Feral Cat Feeder
-Colony Manager
-Substitute Feeder

Transportation:
-TNR Cat Transport
-General Transport
-Cargo Transport

Feral Cat Trapping:
-Trapping
-Pre/Post Surgery Care
-Community Coordination
-Mitigation

Fostering Adults/Kittens
-Basic Foster Home
-Special Needs Foster

Pet Adoption Fairs:
-Manage or Assist a Fair
-Adoption Counselor

General:
-Answering Questions
-Education
-Training

Secondary Volunteer Opportunities:
Public Relations:
-Adoption Promotions
-Communications
-Creative Writing
-Media Relations
-Public Interface Assistance

General Administration
-Data Entry
-Graphic Design
-Photographer
-Volunteer & Donations Coordinator
-Web Design / Maintenance

Fund Raising
-Campaign/Event Manager
-Event Planner/Helper
-Grant Writer

Special Projects and Lots More
-Shelter Assistance (cleaning & socialization)
-Behavior Advisor
-General Labor / Help
-Provide Storage Space
-Legal Advice
-Sewing, knitting, crocheting
-Groomer
-Carpentry / Construction
-Vet Service
-Vet Tech Assistance
-Special Events (both)

The information above can be found on the official website of Cat Resource Center. For more details about the organization and to find out how you can volunteer, please visit their website: http://www.catcenter.org