StumbleUpon is an interesting way to discover great websites.
Their site says it better than I can..."Using search engines to locate relevant content typically means hunting through pages of results. Rather than searching for quality web sites, StumbleUpon members are taken directly to web sites matching their personal interests and preferences."
So mail your postcard and then go "stumbling."
Important note: these sites can be addicting and time passes very fast when you're cruising around them.