How to know if it was bundled before?

http://www.steamgifts.com/bundle-games
Keep in mind that only one person manages this list and not everything appears there immediately.

This is the list of bundled games.

I'd just like to point out that the bundle list isn't always updated. It often misses the recent bundles and, sometimes, games added to the bundle afterwards. You might wish to check also http://isthereanydeal.com/. In case of giving away a package, best to check each item in the package (if any item has been bundled, the package should be considered as bundled as well).

isthereanydeal tells you if the game was in a bundle.
and its lower price to date.

All of the above plus install Enhanced Steam.

thx guys