Dakota County's mobile app works wonders. I understand it is a bit wonky from time to time, but it has lots of the stuff that people use/want most right at their fingertips - their account, the calendar, the catalog and books.
I am impressed with ELM's app too. (Isn't Jennifer Hootman a gem?). I think it would be great if the school libraries that have iPads would put the ELM site right on their homepage. I know that they use these resources extensively, to have the right at their fingertips would be great.