Pagespeed caching css, annoying to develop

Alister is right. There are other two ways I know to do this. With a .htaccess shared through many domains and you want to disable PageSpeed only on a single domain, you can add to the bottom of the .htaccess file:

<IfModule pagespeed_module>
  ...
  ModPagespeedDisallow http://www.example.com/*
</IfModule>

It means that you can have two domains, one for the developement (ModPagespeedDisallow) and one with ModPagespeed active. Never tried but should it works, avoiding visitor getting a not optimized page during development.

Or you can add ?ModPagespeed=off to the url as stated on mod_pagespeed FAQ.

According to http://code.google.com/speed/page-speed/docs/using_mod.html#htaccess you can turn off the module with the line ModPagespeed off in a .htaccess file.

The best solution would be to have a non-live development environment that didn't have mod_pagespeed on at all, or where it could be added only for some final testing.