This page contains different firmwares for Asus RT-N16 (from both Asus & Oleg).
Tomato USB Mod firmware: tomato-K26USB-1.28.9054MIPSR2-beta-Ext.rar – this one I am using currently.
Tomato USB Mod firmware: tomato-K26USB-1.28.9050MIPSR2-beta20-Ext.rar – this one I was using for last 4 months – very stable and solid firmware.
Oleg’s firmware 1639: RT-N16-22.214.171.124-rtn-r1639.trx.zip – this one I was using for last 6 months – very stable and solid firmware.
Asus firmware FW_RT_N16_1017.zip – official firmware from Asus. Very unstable and contains a lot of bugs.