For travel days and if the dress code is relaxed enough to allow polo shirts, nothing beats a technical fabric polo shirt; either long or short sleeve. Usually found as "golf shirts". The bargain of the bunch is the Target-specific Champion C9, which can be found from $14-25 depending on the sale.

+1 for the Brooks Brothers no iron shirts for dress dress shirts, btw. Lots of the "travel" shirts (like ExOfficio) are not formal enough and if that is the case with the dress code, I go with the aforementioned polo shirts...