I have cooked up a compressor design that uses 3 2N7000 NMOS FETS and one op amp. Its very easy to build and uses a LED as a peak detector and compression level indicator, as it lights up with varying intensity proportional to compression level.

Using a MOSFET as a voltage controlled resistor requires very small signal levels or it will cause distortion. To solve this, I employed negative shunt feedback to buck the input signal at the input node. This results in signals in the range of ten mV across the voltage controlled resistor.

LINK to Schematic:

http://circuitsaladdotcom.files.wordpress.com/2012/10/simple-compressor.gif

I am posting a schematic of my approach to using the PT2399 for a delay. I can get long .7sec repeats with little noise and I don't need a compander! I did some different things than the standard circuits out there. The trick in my design is using a much larger cap (.47 uF instead of .1 uF) between pins 9 and 10. This gives an increase in signal output but the noise stays the same. Then I reduce the output at the wet dry mixer and the noise goes way down. Also the wet/dry mixer is the op amp between pins 13 and 14.  Instead of using this Opamp as a filter, I used a switch cap filter IC, but all kinds of other low pass filters could be used. I must say that it really does the job and only uses 1 cap to set the cutoff freq from 1Hz up to 5KHz. Check out the audio sample.

I thought someone might also be interested in my compressor design. It originated from looking at the Orange squeezer, but has more features, namely, totally discrete signal chain, gain control via a H11F1M opto FET and uses a zetex ZXCT1041 current sensor as a ideal full wave precision rectifier. I also have a simple op amp implementation that works fine(for rectifier) but the ZXCT1041 is really great for converting signal level to control voltage- it works reliably up 50Khz or so. The circuit provides control for compression level and out level. Its quiet, has no critical adjustments and uses little power.

I am new to this forum and thought someone might find my amp design interesting. Its a guitar amp designed for busking and uses a cordless drill or SLA  battery for power. It has discrete circuitry until the final amp which is a TDA7360. Its relatively simple but has all kinds of potential for tweaks and I am sure others can come up with improvements.
I have attached the schematic. Sound samples, circuit variations and pictures can be seen at: www.circuitsalad.com