To share internet access, you first need to have internet access, and be allowed to share it! Most common broadband internet providers, such as Cox Cable(home level) or SBC DSL, do not allow sharing with their standard accounts.
For a small premium (typically $10-20/mth) you can use a provider that explicitly allows sharing. Some national providers include: Speakeasy, DSLExtreme and Megatpath Networks. It may also be possible to upgrade an existing account to a business account that permits sharing. For example, Cox cable currently (Sep 04) has a Home Office package for $89 which allows sharing. Time Warner has a similar deal starting at $109.
It may also be possible to connect your location to an existing SoCalFreeNet location. This will cost between $300-500 more for extra equipment, but you will avoid all ongoing monthly fees.