Some things I use to test mental ability as well as train it are: BrainWorkshop (A free dualNback program), Cognitivefun.net (A site with assorted tests and profiles including everything from reaction time, to subitizing, to visual backward digit span), Posit Science's jewel diver demo (a multi-object tracking test), and Lumosity.com (brainshift, memory matrix, speed match, top chimp. All of these tests can be found for free on the internet).

Subjectively the regular use of these tests has increased my metacognitive and self monitoring ability. Anyone have other suggestions? How about tests one can do without the aid of external devices?

In complement to determining whether one's brain isn't in its best state there is the question of how to improve or fix it. Keeping with the general spirit of this thread, what are some strategies people use to improve their cognitive functioning (as it pertains to low level properties such as short term memory) in the short term without the use of external aids? A few I use are priming emotional state with posture, expression, and words, doing mental arithmetic, memorizing arbitrary information, and doing the above mental tests.