Which online tools would interest groups most likely use to recruit direct civic participation among the public

The most effective ones are social networks, specific sites and information by emails.

Social networks will reach an absurd number of people and groups interested in civic participation. Because they have great power of reach and dissemination. Specific sites will be the online places where the recruiting issue can be emphasized. And they can still be a trustfull source of detailed information. Information by emails are related with the public filtered through the internet or groups that you maintain frequent contact with massive strategic content.