Before launching I do:

* Minify Html, Css, Js using the YUI Compressor

* Compress images using tinypng.org

* Run the tests I wrote during development

* Do a final stress test using blitz.io

* Generate a XML Sitemap for search engines and edit the robots.txt

* Run a spellcheck using checkdog.com

* Setup monit to make sure my app restarts after a crash ;)

Guess that's it ;) Funny side story: I launched my weekend project receiveee.com last week and failed big when moving to production. During developing I ran the app under admin, but I ofc didn't when moving to production. BUT, my app includes a smtp server which couldn't run on port 25 without admin rights. No error appeared, but not a single mail arrived. Even took me 10 minutes to find the problem :D