There is a yahoo group and one thing in it that I find very useful is Dan Tayloe in a presentation (in video here too http://www.azscqrpions.org/RCFiltersWEB.wmv) went through the design of the audio filters, that you could easily adopt to other applications.
Dan pretty well took the design apart and did a good job adding to the design but in the presentation I think missed the point of the original from Mike King G3MY and that was to build a rig using just one single IC and no other semiconductors. So if mentioned nowhere else it is here. Do more with less.
The project design brief was as a club kit to reduce the different unique part counts which is great but this does mean if not building as a kit, which I would recommend if not regularly homebrewing, that you can make substitutions too. e.g. I bought a pile of NE5534 single low noise op amps a while back and the design uses NE5532 duals but you can use two singles instead. This obviously means the unique part count increases.
I am also a bit baffled about the comments in the group about CA3086 as the CA3083 is almost the same, pin changes but very much still available, even in SMT form and would work just as easily.
CA3086 data sheet http://www.intersil.com/data/fn/fn483.pdf
CA3083 data sheet http://www.intersil.com/data/fn/fn481.pdf
The more modern HFA3046 is the same as the original CA3086
OK despite being near freezing in the shack, just sorted components ready for a Manhatten build. I am short one or two items but an order with Farnell or Jabdog should sort them out.