If - like me - you're working on a responsive website project which still has IE8 in the browser matrix, you may find my failsheet helpful during development. It simply lists all the techniques that IE8 does not support natively and keeps you on your toes when you're about to get into a CSS3 feature flow extravaganza.
It doesn't say anything about possible fallbacks and/or polyfills, those are left to your judgment. Just keep
in mind that it's often possible to use :first-child instead of :last-child or get approval for a rendering without text-shadow in IE8 from both design and client, and I suggest to try those avenues before you venture down the Selectivizr, CSS3PIE, respond.js etc. route (which each come with their own pitfalls).
Enjoy and please feel free to comment about stuff I missed or which you think is unnecessary!