For recruiting subjects (via internet) for lab experiments:
ORSEE (by Ben Greiner) is a web-based Online Recruitment System, specifically designed for organizing economic experiments. There is a test system online where you can log on without registering. ORSEE will be installed on a local server (ExLab maintains your subject database on their server).
A user manual and installation notes are available as well
CASSELL from CalTech (via internet). The CalTech lab has been developing both experiment management and experimental software in the past several years. They are due to release a new version of the experiment management/recruiting web application very soon.
For designing, programming and running experiments:
LabSEE -a new experimental program. This program uses Java as programming environment to conduct experiments over the Internet. The functionality should be similar to Z-tree. The beta version and tutorial will be available soon. Now, you can download version 0.5 with no documentation.
In addition, some bigger labs (SSEL, CASSEL, ICES, ESI) offer code or programs for free download.
For instance: Veconlab provides about 50 on-line programs for different types of markets/experiments. jMarkets is open software to run markets experiments online.