Press-and-Peel(tm), photoresist, Sharpie, nail polish...
I have used this method for etching some fairly fine lines when fabricating a microstrip microwave filter using Tom Gootee's method linked to below. My two cents on this is the fact that the type of toner you use matters. In an admittedly small sample set of two different printers, the genuine HP microfine toner performed far better than the generic toner that was installed in a second printer that we tried. We used the Staple's glossy inkjet paper, and with the HP toner, it worked quite well.
Also, the etching solution of 1 part muriatic acid to 2 parts hydrogen peroxide is worlds better than the ferric chloride solution as it is clear and doesn't stain everything it touches. It is also available locally (hydrogen peroxide is in every drug and grocery store, muriatic acid can be found at almost any hardware store).
Thankfully, we worked in a school lab that had access to pure acetone for cleaning off the traces, so we didn't have to resort to foul-smelling nail polish.
- Direct Etch PCBs These guys are selling a product for toner transfer, might be good or bad, ( how about a review by a user? ) but in any case they also have a bunch of very useful tips.