Gnash

Gnash is a free and open-source alternative to Adobe Flash Player. Gnash, unlike Flash, is easily portable, and can be used on x86, x86-64, and PowerPC computers. Adobe does not make a version of Flash for PowerPC Linux, and no version for any operating system on x86-64. This makes it useful for people who run Linux on older Macs or PS3s, or who want to use 64-bit browsers and 64-bit operating systems. It is considered a high-priority project to the Free Software Foundation.

Support
Gnash does not fully support the latest version of Flash, so some games or animations may not work right. It supports most of Adobe Flash 7 and 8, but only some of version 9.