Yeah, Layton is awesome (still need the new ones), Picross is too, Meteos is probably my favorite DS puzzle game (if you want to call it that).
Hotel Dusk is probably my favorite DS game overall and I've been dying for a sequel. Last I checked the new one didn't look like it would be coming state side

However, it's releasing in Europe in September, so maybe that will be good enough.
Anyway, there are a lot of games I could recommend, but just take a look at my collection for yourself (or most of it, anyway). Hopefully the forum software won't compress it so much you can't read them all
If you're going for puzzlers, though, here are a few obvious recommendations: Tetris DS, Professor Layton, Planet Puzzle League, Picross DS, Meteos, Mario vs DK 2, Zookeeper (this one is a Bejeweled clone, basically)...and that's about all I can think of at the moment.
UMK has been out for some time. I picked it up when it was pretty new and sadly wasn't too impressed. Though it's a good port, overall.