The above posters are correct. However, I'd like to add, any avatars and themes downloaded with Playstation Plus are yours to keep - forever, even after your subscription has ended.
To take it one step further, anything you purchase during your PS+ subscription is yours to own forever. So when DLC is offered at a 20% discount (or whatever), if you purchase it, the DLC is now yours. If the DLC happens to be for a "free" PS+ game, you may no longer have access to the game, and thus your DLC is useless unless you purchase a copy of the now expired game.
When was the last time PS+ bothered to grace us with free avatars and themes? Oh ... I forgot ... the community "spoke" and decided we didn't need any of those with the introduction of the IGC.
Does this mean I can't play it offline? I mean with my internet on the PS3 turned off? I guess it makes sense not to incase your not a Plus member anymore. I wanted to subscribe just to get the free games but since I can't keep them I leaning towards gamefly...Makes sense for those who don't care about the discount on digital games(I rather buy disc-based).