Project:Open Source SDR

The really cool bit about the USRP is GNU Radio. But you don't need a USRP to take advantage of GNU Radio...

http://wwwhome.cs.utwente.nl/~ptdeboer/ham/sdr/

Open Source SDR
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Poor man's USRP http://www.lightlink.com/mhp/iq/

Commercial products:

http://www.signalhound.com/index.htm

http://www.ettus.com/products