Entware is described as a modern optware replacement. Most of entware's packages are taken from OpenWRT, but others are unique. If you are considering to install optware, you should try entware.
This instruction is for ARM or MIPS devices only.
1. Turn on jffs.
In Tomato, enter the web interface, go to "Administrator", then "jffs", check "Enable". Type in the code below into the "Execute When Mounted" box.
mount -o bind /jffs /opt
After reboot Tomato will mount jffs partion to opt.
DD-WRT need to put the above command to the startup.
2. Perform the entware install. The script will install entware to /opt.
On ARM devices
wget -O - http://pkg.entware.net/binaries/armv7/installer/entware_install.sh | sh
On MIPS devices:
wget -O - http://pkg.entware.net/binaries/mipsel/installer/installer.sh | sh