I came across a good roundup of Best Apps of 2010 in Google Apps Marketplace by Klint Finley of Readwriteweb. These are the "top installed" apps of 2010. The list is as follows:-

1. Manymoon – Project Management
2. Insightly – CRM
3. Zoho CRM – CRM
4. Aviary Design Suite
5. Mavenlink – Project Management
6. Outright – Accounting & Finance
7. MailChimp – Sales & Marketing
8. RapidTask – Project Management
9. Insync – Document Management
10. myERP.com – myERP.com

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