I <3 the Opscode Bento project. I use the Amazon S3 hosted images for pretty much all of my Vagrant boxes. When I started to use RHEL, I didn't want to make an exception... Fortunately Bento allows you to build your own RHEL, OSX or Windows boxes using Packer. This is how I built my RHEL 6.4 x64 box, but this process should work for any other box you want to build manually...
If you are on OSX, you can install Packer using Homebrew:
brew tap homebrew/binary brew install packer
If not, you can follow the instructions on the Packer's website
Clone bento and add your RHEL Server ISO
https://github.com/opscode/bento.git cd bento/packer mkdir iso #cp your rhel-server iso here... it should be named rhel-server-6.5-x86_64-dvd.iso
Build your RHEL box
packer build -only=virtualbox-iso -var 'mirror=file:///`pwd`/iso' rhel-6.5-x86_64.json
This takes a little while so go and get some coffee...
Add to Vagrant
cd .. vagrant box add rhel65x64 builds/virtualbox/opscode_rhel-6.5_chef-provisionerless.box
Then to test it, create a new Vagrant image that uses the new
cd <a tmp dir> vagrant init sed -i '' 's/config.vm.box = "base"/config.vm.box = "rhel65x64"/g' Vagrantfile vagrant up vagrant ssh vagrant destroy