Flash is a very fun tool for most website designers. Recently, though, developers have been using it for evil rather than good. There is hope, though. You can easily choose what Flash you see (or don't).
Download and install FireFox. If you have it already, you're 50% of the way there.
Step2
Download and install the FlashBlock plugin for FireFox. Restart FireFox.
Step3
Visit a website such as YouTube or Google videos. All flash content will appear in a gray outlined box with an arrow in the middle. This will decrease load times of websites, since the Flash content won't be loaded until you tell it to be.
Tips & Warnings
If there are websites that you want to always allow Flash from, click on -> Tools -> Add-ons -> FlashBlock Options, and add the website to the allowed list.