Mac: While learning keyboard shortcuts certainly puts you on the fast track to obtaining your official productivity geek credibility card, it's not for everyone. OptionSpace is a little app for OS X that allows you to instantly pull up a search menu to find various menu bar items just like your would with Spotlight. When you're in any app, you can tap Option+Space to pull up a search menu, type in a couple letters of what keyboard shortcut or menu bar item you're looking for, and the OptionSpace shows you results. Tap Return and it executes that shortcut for you. It works something like a combination of OS X's built-in Help menu and Spotlight. This allows you to access menu items without touching your mouse, even if you can't remember the shortcut. If you're not great at remembering shortcuts for menu items, OptionSpace is worth a look.
The pricing system for OptionSpace is a bit convoluted though. It starts with a 10-day unlimited trial, but after that, you get seven uses per week for free. If you want to use it more, you'll need to pony up for the licence, which is currently $US15 ($21), but bumps up to $US19 ($26) at the end of the year. It's a nice system in that you get to try before you buy and the free tier makes it accessible for casual users, but it does get a little confusing. Regardless, if you can't seem to remember keyboard shortcuts to save your life, OptionSpace is worth a look.
OptionSpace (Free/$US15-$19 [$21-$26])