By far, this site is extremely comprehensive and shows built sluices, dredges - all sorts of things. I am including this site because it gives pictures of the equipment and some people may not be aware of what these contraptions look like. It describes how to build a sluice but does not, as far as I can tell, show plans.
The verbal descriptions of how to build these things are good. There are also many links to places where you can purchase prospecting equipment.

There is a set of plans and a drawing of an old time rocker box. This is the type I modeled mine after.
http://nevada-outback-gems.com/design_plans/DIY_rocker/Rocker_box.htm

A number of these projects would run into some money. The PVC, pumps, hose, etc would have to be purchased at a home improvement or mining store. Nevertheless, these pieces of personally fabricated equipment could be made for less than retail.

There are a number of links at the bottom of the page where you can get other information from Nevada Gems.

http://nevada-outback-gems.com/design_plans/DIY_equipment.htm (click on the link)