The low cost of DS game development and the extraordinarily high popularity of the system make the DS an excellent way for new developers to find an audience. 5th Cell is a notable company who has done great with the DS -- which is why they've made this Gamasutra list of breakthrough developers. Level-5 has been huge for a while, thanks to Dragon Quest VIII, but Professor Layton upped their profile significantly.
Have any developers come to your attention since you started playing the DS? Old or new, have you become a fan of a company for their DS output? We're sure there are some out there without the number 5 in their name.