Vincent Cojot, one of our Snort Community members has taken it upon himself to maintain the list of RHEL5 compatible RPMS and SRPMS in both i386 and x86_64 formats. These include libpcap, daq, libdnet, and of course Snort itself (18.104.22.168). DAQ and Snort 2.9.0.x will not work on RHEL5 because of the older libpcap libraries, so you will either have to compile your own libpcap, or use the RPMs below.
So if you are on RHEL5, and you want to upgrade to the latest and greatest version of Snort without compiling, see Vincent's RPMS.
Sourcefire, however, makes no endorsement of Vincent's RPMS or their contents. Use at your own risk. Sourcefire will always recommend that you download and compile Snort, from the source code, available at http://www.snort.org.
Take a look:
Hopefully this will help those of you at RHEL5.
UPDATE: We created a page at Snort.org to help you if needed.