Producing biomaterials that are very hard to make purely synthetically, or are very valuable (or both - see spider silk) by using biological systems in biobricks is a very appealing idea. There are several "types" of materials that could be made, each with their own challenges and benefits.
This could be drugs, for instance, and there are several specific issues that require attention. Would a Synthetic Biology approach improve sufficiently on a standard genetic engineering one? Drugs like insulin for instance are already widely and cheaply produced. Perhaps there are drugs out there we'd like to make that are resistant to standard GE approaches?
This field holds the most promise with regard to the motility of bacterial production.
Fibrous materials are some of the most useful to us; textiles, nylon, spider silk being popular examples. Production of such is probably impossible directly as fibres, and is almost certainly out of our reach for this project unfortunately. Again, see the motility page for reasons for its difficulty.