Nunavut, Nova Scotia and Quebec are pretty much my favorites in Canada.
Back south of the border to the original topic, special mentions to:
-New Mexico has awesome history behind it (it's a pueblo people symbol making it one of about *two* US states flag that acknowledges the Natives),
-Maryland gets cookie points for not being a stupid state seal on a field of whatever color (and being generally pretty cool),
-Texas isn't bad (at least has the merit of being simple)
-Indiana as noted above is nice.
-Cookie points for Ohio and Tennessee for not doing the state seal thingy.
-Special mention for Massachusetts because their state seal is relatively well designed enough (compared to...all the others) to result in a semi-decent flag. Also see "acknowledging the natives"
A special place for Vermont for not taking the awesome Green Mountain Boys flag and instead doing a stupid state-seal-on-green/blue design like almost everybody else.
And a final special mention back in Canada for the flag of French Ontario, which is pretty cool in my opinion.