I have spent a few months developing and selling flash games getting out two titles; Bubbles Pops and Cocomono both available in the GAMES section of this website for some time now.
Although I am not an expert, I would say that it is not too difficult to earn some extra money developing flash games and selling them directly to the sponsors or through FGL portal. I would say, that the most important thing, apart of good game, is the fact of develop something that can attract the attention of sponsors, for example, some king of clone of one of the latest hits in the smartphone markets.
I have published these games under the name of Alienline Softworks, which is going to be the commercial name under which I am going to publish all my semi/professional projects.
Here are videos of both games:
Bubbles Pop
Cocomono
Hope you like it
;)