There is not a good selection of electives after you've completed your second (traditionally your first) year. Let's face it: most of the best electives are offered during the day, since most law professors are not too thrilled with the prospect of teaching night school.
Maybe this is true at lower ranked schools but I know GW offers quite a bit of evening electives each semester. Also, PT students can take classes in the day if they are dead set on a specific class.
Lastly, every lawyer I have spoken to has told me that electives should be used to better prepare you for the bar, let the firms train you in the particular field of law you are interested in. That being said, the important electives will always be around for PT students to take.