Have a look at the sub-woofer controller and input buffer and high-pass filter projects on my website - use dual op-amps though. If you want more modularity and are stuck with single op-amps I have the pick-n-mix active crossover project (use the 2nd-order filters). I have a simple program on the utilities page of the website to calculate values for the filters.
Check out the old standby book on Op-Amps by Walt Jung.
I might recommended a newer device to work around. The good 'ol 71, 72 series were fine in the 80's but 30 years of design have improved op-amps to the point of high fidelity.
Might also check out Elliot Sound Products. Check out the articles Sid Linkawitz has posted.