I was typing to a friend online, and I was saying something about vaginas, don't ask why, and I noticed that the squiggly bad-spelling line came up under vaginas. I figured that it must not be the proper plural form of the word, so I looked it up. Sure enough, the plural is vaginae (click here if you want proof).
Vaginae is quite lovely, actually. It sounds French.
Glad I could educate tonight, and if you click over to the dictionary page, be sure to click the sound thingy where the guy pronounces the word because he sounds mad creepy.