Zendesk
(User)
Zendesk is a very popular customer support service (helpdesk).
Salesforce.com
(Contract)
Salesforce.com is a very popular cloud based CRM.
Use FoxWeave to easily Sync Users in Zendesk to Contracts in Salesforce.com
Cloudant DB

FreshBooks

Google Forms

Google Mail

HTTP

MailChimp

MongoHQ DB

MySQL DB

Oracle DB

OnePageCRM

PostgresSQL DB

Salesforce.com

Sendgrid

MS SQL Server DB

Webhooks

Wufoo

Twilio

Twitter

Zendesk