Harvest for Salesforce
Native Salesforce.com integration with the Harvest API. Features Harvest Clients, Contacts, Projects, Tasks integration with Salesforce Accounts, Contact, Opportunities, Projects, and Users.
To install the unmanaged package: Harvest for Salesforce (Open Source)
To use the source code with a Salesforce org: [How To Use Github and the Force.com IDE] (http://blogs.developerforce.com/labs/2011/04/how-to-use-git-github-force-com-ide-open-source-labs-apps.html)