I'm not a big link blog guy, but Martin Fowler's note/outline/draft material for an upcoming book on Domain-Specific Languages is worth checking out at your earliest convenience. I've been impressed.
Lest you be tempted to pick sides for or against DSLs (really not the point of Mssr. Fowler's book), or to postpone thinking hard about them, consider: DSLs are already merging with with 'traditional' languages and APIs ... it is likely that this trend will continue, with the result that DSLs will be a fact of life in the 'standard model' approach for many types of applications.
So it's probably useful to get a grounding in what they can really do, how they can best do it... and how they can best not interfere when they shouldn't.