|There's no alternative to Adobe's Flash Player that I know of. |
Adobe Reader is a different kettle of fish because that's just a document reader, allbeit a particular type of document, so creating an alternative is not restricted by patents.
Flash Player technology, however, is robustly protected by Adobe who bought it from Macromedia a few years ago. Any alternative would still need to use parts of that technology, and Adobe wouldn't tolerate that.