Free Software for Managing a Lean Startup

I recently met with a former student, Sunil Nagaraj, founder and CEO of Triangulate, a Silicon Valley-based startup that's just launched its first product, Wings, a Facebook dating application. Sunil, who has embraced lean startup management practices, showed me a set of free software tools his team is using to build and manage its product. Here's Sunil's list along with his thoughts about how he uses the software. Please extend the list in your comments to this post.

• Google Apps (standard edition) - Free email and calendaring on your own domain name
• PivotalTracker - Free project management tool perfectly suited for managing development features for a small team 
• Dropbox - Free "fileserver" for sharing any files across team. All team members get a "My Dropbox" folder in "My Documents" which is always up-to-date
• SliceHost - Incredibly cheap server-space -- lower-priced plans than Amazon for getting started -- $20/month with no setup cost for server that should handle most consumer internet sites until user traffic really takes off
• Viral Marketing Calculator - Amazing calculator for determining user growth 
• Twitter - Every entrepreneur must be on Twitter to stay "plugged in" and to market his/her product
• VNC, Putty, Filezilla - Free tools for screen-sharing, SSH/telnet, and FTP respectively

Addendum: This post from Peldi Guilizzoni on the Balsamiq Company blog significantly extends the list above and provides very useful commentary. It's a must read for startup teams. Thanks to Jeremy Levine for pointing it out!