3D printing is projected to be a $782 million dollar industry by 2013. Z Corp, of course, currently controls the lion share of the market. We're still in the infancy of the industry. It will be interesting to see other companies grow in the near future to challenge Z Corp.
The leading technologies in 3d printing are ink-jet, fused depositio modeling, selective laser sintering, and stereolithograph solid imaging.
3D printer prices will continue to decline although we're still a good bit away from seeing this technology enter into the cusumer market. Open source projects like RepRap and Fab@Home may shorten that time though. Who knows, by 2013, you may be seeing 3d printers at Best Buy.