I run a printing company, so it's important that I get that out of the way before talking about print and snail mail. A lot of my real estate clients have jumped on the Internet bandwagon and have adopted an almost religious belief that anything on paper is bad and anything on the screen is good. Like any single channel strategy, this myopic view can do a lot of damage to your brand.
The fact of the matter is that real estate is a local business, the average farm area is around 1000 houses and how many agents do you know that have the email addresses for every resident in their farm area? Email marketing and banner advertising are great, but they don't replace the need to stay "top of mind" for your local area. The three best tools for this are boards, letterboxing and direct mail.
It's just as important to develop a consistent and strategic plan for your brand and salespeople to own the letterbox as it is to have a great website in the business. I saw this great article about snail mail and the effect that dropping it has had on some small businesses in the States.