This past weekend, I blew out my linux install to check out Redhat's Fedora Core 3 and for the 3rd time went though getting dsniff 2.3 installed with the WiFi patch.  Everytime I've done this, I've forgotten how and had to re-learn it.  Here are the steps.

Setup your system

1.  Install Redhat Fedora Core 3 with 'All' packages (feel free to try with less, but I've got the drive space and wanted to deal with as little dependencies as possible).
2.  Get the latest MadWifi drivers out of CVS:
     cvs -z3 -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/madwifi co madwifi
3.  Compile and reboot
4.  Make sure your wifi card is working.

Install DSniff

4.  Download and compile/install Libnet-1.02a: 
     http://www.packetfactory.net/libnet/dist/deprecated/libnet-1.0.2a.tar.gz
5.  Get libnids 1.18 out of sourceforge: 
     http://sourceforge.net/project/showfiles.php?group_id=92215&package_id=97542&release_id=191323
6.  Download the patch to allow for wireless dsniffing in rfmon mode:
     http://airsnort.shmoo.com/libnids-1.18-snax-prism-modified.diff
7.  Patch it, then compile/install:
     patch -p0 src/libnids.c ~/wifi/libnids*.diff
8.  Make and install dsniff:
     http://www.monkey.org/~dugsong/dsniff/dsniff-2.3.tar.gz

DSniff

9.  Put your card into RFMON (monitor) mode:
     iwconfig ath0 mode monitor

Couple of points/questions:
     -It is possible to get it compiled with newer versions of libnet (prepare for a huge headache).
     -I have not found a newer patch for libnids 1.18 - let me know if there is a better way..
     -I've found dsniffing wifi with the '-c' option helps when you are far from the base station (you may only receive half the trans because of signal power).
     -Has anyone figured out how to set the sensitivity?  I've tried, but I can never see any change - ex: iwconfig ath0 sens -80, etc.