Even on Windows these 'RAM Recovery' programs are of very, very questionable benefit, see http://mywebpages.comcast.net/SupportCD/XPMyths.html http://www.windowsitpro.com/Article/...1095.html?Ad=1
All you're essentially doing is forcing a large amount of the data in RAM for running programs into swap space which is literally about 1000 times slower to read from because its on disk.
Linux will automatically use almost all your available RAM for a disk cache (which is why many people think Linux is a memory hog because it always appears to be using all the RAM) and will then feed RAM to programs as they request it. This RAM used for the disk cache is not considered 'in use' because it can instantly be made available for overwriting by any program requesting more RAM, because its just a copy of what's on disk.
Trying to use some kind of 'RAM Optimiser' which requests a huge amount of RAM then frees it again to give the illusion of 'free RAM' would probably dramatically decrease the performance of your computer. It would force the system to dump pretty much all the disk cache and force most running process' data into swap space. In other words you've basically moved everything out of your nice, fast RAM and onto slow disk. And its all unnecessary, there is no need to do this before starting a game or something because Linux will allocate it the RAM it needs.