i built a few jobs boards (http://djangojobbers.com, http://railsjobbers.com). If I see any interesting django job published I apply to it (usually pointing out you are the system developer grants you some extra points).
Also I built a password manager (https://identee.com). I am finishing a pro version of it (with a Command Line Interface client, instead of browser based), which is the one I am using. Indeed I am the only one using it since its not live yet ;-)
Well here is my journey.
A few months ago, I built a vertical jobs board platform, free for developers and paid by companies announcing their job offers (yes another one).
The numbers:
I launched during summer and have made around $200.
Have 1125 developers subscribed to daily alerts
Have processed around 1500 applications for 81 jobs posted (most of them through 100% discount tickets given away)
The idea was not very well thought, but something simple to start with.
I used it to start gaining experience and also to start building a reusable code base (mailing, billing, etc) that would let me move faster with future products, not expecting to make any money at all from it.
As a single founder/developer/designer/sysadmin/marketer/support guy etc, I found it very hard to accomplish, but very rewarding once it was launched.
I also have boards for javascript, php, java, android or ios, but with not a lot of subscribers, so they are free for publishers for now. The links are http://php.jobbersnet.com, http://ios.jobbersnet.com, etc
Now I am getting ready to launch a new thing (identee.com) to help low level users increase their security by storing their usernames & passwords encrypted in the cloud.