if you get any dependency errors, fetch the required RPMs from http://mirrors.kernel.org/centos/5/os/x86_64/CentOS/ and install manually with the rpm command. don't be surprised if the dependencies have dependencies, normally yum would sort that out automatically.
if your application is 32bit, then you'll need to install 32bit ODBC instead of the 64bit stuff above.
if you ARE on Red Hat Enterprise Linux without a RHN subscription, you really really should be on CentOS instead, its a 100% compatible distribution rebuilt from Red Hat sources with the branding and redhat network subscription stuff removed and replaced with open yum repositories.
btw, i'm offline til next week. have fun with that.
Yes, its RHE without subscription. Hard time!
On a different box, I did the other way and installed unixODBC64 using the above links. There were some libtdl* dependencies and installed package libtool-ltdl-1.5.22-7.el5_4.x86_64.rpm for that. unixODBC is done with the above method.