I know this is late but maybe for other reading the thread...
I got the open logic sniffer which is open source hw built for SUMP. $50 for the board from Seeed ($70 from sparkfun). Probes were a few bucks more and I found a reasonable case to hold it for <10. 16 channels. The current incarnation claims capture rates up to 200 mhz. The java based client is ok though suffering through getting the right version of java on my machine was an exercise in patience.
Here's the main page - http://dangerousprototypes.com/2010/02/25/prototype-open-logic-sniffer-logic-analyzer-2/
I've had it a month and so far I've used it for some mundane stuff - debugging i2c, spi, lots timing stuff - it worked perfectly. Given that my all in cost is about $75, I am way happy with it.