Creo Elements/Direct Modeling Express
||A free CAD application, formerly called "CoCreate Modeling Personal Edition". CoCreate was spun off from HP's Mechanical Design Devision in 2000, then bought by PTC in 2007.
The free Express edition of Direct Modelling is almost fully functional (except for the fairly niche parts like sheet metal). Its primary limitations are: an internet connection is required to run it, and assemblies cannot have more than 70 components.
||Primary download. You also need to register for a free account to use it.