I recently discovered a great free service from BT where you can advertise your company online for free.  Here's AdStorm's entry by way of an example - Advertising Agency.  It's called BT Tradespace and they offer companies the opportunity to publish a mini website advertising your business, the products you offer, you can write a company blog and various other details - great in particular for small companies or for designers / freelancers maybe who don't want to go to the expense of developing their own website but want some kind of presence to advertise themselves online.