C.,
After my first was born, I was a member of a bf support group (basically, a bunch o' moms that sat around chatting, and we'd usually have one topic of the day that revolved around bfing). One of the topics was uneven breasts, and the lactation consultant explained (hopefully, I'll recall this correctly) that for most women, one breast produces faster (quicker letdown for hungry babies) and the other is the bigger producer, always seeming larger than the other.
Those of us in the room, sat staring at each others' chests, comparing the two. ;-) You tend to notice it more because you're kind of focused on "the girls" right now (and see yourself naked), but nobody you pass on the street is going to drop their jaw in disbelief and call you a "freak show" because one is bigger than the other.
It can also vary if you alternate feedings. It's good to make sure that the breast is emptied with each feeding (to avoid plugged ducts, etc.), so if you feed on the left for the morning feeding, of course your right one will seem HUGE for a while.
Additionally, some of us tend to feed more on one side or the other, based on our dominant hand (I'm right handed, so I prefer to nurse on the left, so I subconsciously go there first). With increased usage, this could very well lead to the aforementioned larger producer.
Oh, and they DO go back to normal after weaning. Well, usually a lot more saggy, but at least their even! ;-)
Congratulations on your fabulous boy, and good luck with the continued nursing!
M.