A bunch of us in the IRC channel ( #idevgames on freenode ) decided to have a three hour mini-contest with the theme of "construction" today.

Three of us presented something more or less "playable" at the deadline; you can download the entries here:

freaksw - "Road Construction"
binaries: http://www.freaksw.com/temp/RoadConstruction.zip
source (RealBasic): http://www.freaksw.com/temp/RoadConstructionSrc.zip

ThemsAllTook -
binaries: http://www.sacredsoftware.net/temp/Construction.zip

OneSadCookie - a semi-ripoff of "UpWords"
binaries: http://onesadcookie.com/~keith/Construction.app.tar.bz2 (known not to work on 10.3)
source (Ruby, ObjC): http://onesadcookie.com/svn/repos/Construction (may contain post-contest fixes)