Sep 05 - Zoho Writer Alpha
Oct 05 - Zoho Planner
Dec 05 - Zoho Writer Beta

Feb 06 - Zoho CRM Released (Product + Service)
Mar 06 - Zoho Creator
Apr 06 - Zoho Sheet
Jun 06 - Zoho Show
Jun 06 - Site24x7
Aug 06 - Zoho Projects
Oct 06 - Zoho Accounts (SSO)
Dec 06 - Plug-in for MS Office
Dec 06 - Zoho Wiki

Jan 07 - Zoho Notebook
Feb 07 - Zoho Chat
Mar 07 - Zoho Meeting
Jun 07 - Zoho launched on iPhone
Jul 07 - Zoho launched on Facebook
Aug 07 - Zoho Viewer
Sep 07 - Zoho Business
Oct 07 - Zoho DB & Reports

Mar 08 - Zoho People
Mar 08 - Zoho Invoice
Apr 08 - Zoho CRM Enterprise
Aug 08 - Zoho Share
Sep 08 - Zoho Docs
Sep 08 - Zoho Marketplace
Oct 08 - Zoho Mail
Nov 08 - Zoho Status
Dec 08 - CloudSQL

Mar 09 - Writer 2.0
Apr 09 - Chat 2.0
Apr 09 - Zoho Mobile

via Zoho Launch Timeline