This morning was a bit unusual in that almost every cyclist I saw on my ride in was a woman! Two on the bike path, and two going up Cambridge street. I saw one guy going the other way, but 5 to 1 is not the normal ratio!
I wouldn't say that seeing other women riding is in any way unusual, but in the summer it's maybe 40% share, and in the winter, group of hard core commuters I'd guess it's about 25% share. I was riding a bit earlier than normal, and on the bike path, but I guess it was more about coincidence than actual trend.