Homebrew PCBs

>  I am looking for the specs for trace width, spacing, and length.

and

 > What I need to know is the clearance between pads.


Isn't trace/pad spacing at least partly a function of the voltage are 
expected to carry?  And, I understand, that as you approach RF 
frequencies, the rules change--or at adherence becomes much more 
meaningful to correct outcomes (e.g., see this from TI: 
http://focus.ti.com/lit/an/szza009/szza009.pdf ).

Have you looked at the manufacturability layout hints provided by PCB 
manufacturing facilities, e.g., this from ExpressPCB:  
http://www.expresspcb.com/ExpressPCBHtm/Tips.htm , or this from a 
consultant: http://www.pdcamerica.com/guidelines.htm ?

There are standards for PCB design, too; a page such as 
http://www.smps.us/pcb-design.html will give you a set of terms to feed 
to Google.

Or punt with Wikipedia:  
http://en.wikipedia.org/wiki/Printed_circuit_board .

All that should give you enough numbers to take any number of sides to 
the discussion.

HTH,
Daniel