Santa Cruz Tech has just released a first draft of their PHP code for Mechanical Turk. This will help take some of the burden off developers trying to code applications that tap into Mturk.
Santa Cruz joins DPA, which has had its HIT-Builder tool out for several months. The two tool sets are very different: HIT-Builder is a full-blown web interface for Mturk, whereas Santa Cruz's work only covers the underlying plumbing.
But PHP is an ideal choice for underpinning a web interface, so one would imagine that their work (released as open source) will eventually power some user-friendly tools.