Jeff Atwood has an excellent article recommending this router.
It can be found here.
In the article is a guide to flashing the firmware with tomato.
The one caveat that I would add is.
You have to reset the NVRAM via key presses which means
I was not able to reach the web address so I was not able to perform the operation via the web admin, so the key press option was my only option.
In performing this process. I found the instructions and distribution of Easy Tomato to be fantastic.
Easy Tomato is by far the best router firmware I have ever used.
It makes the things that should be easy, easy and allows the advanced settings to be found easily.
A couple of examples
You can block any and all adult sites with a single checkbox.(bam)
You can define groups and drag the devices on your network into groups. Yeah I said drag(holy web 2.0 interface batman)
Each group can then have access rules defined for it.
I highly recommend Easy Tomato and the Asus RT-N16 router.