First up -- the MIYA and Brocade series, which is pretty much just a new bunch of designs for the purse variety. They are as good as ever, but each one costs around $70. Seriously, what's up with that?
On the opposite end of the spectrum, the Alumor range is nothing but pure metal goodness in a wide variety of colors. They will run you about $25 which makes much more sense from an accountant's point of view. Go mental, buy the purses! Your DS is worth it.