SSL is Secure Sockets Layer, you may have also seen it called HTTPS (secure HTTP). Basically it means that your traffic to the site is encrypted so people "between" you and the site can't see what data you're sending/receiving. It also is a way of verifying that the site you're on is who it claims to be (and not a rogue server).
If you're ever browsing a site while on a shared network (technically that's everywhere, but especially like in a coffee shop, at work, or at home on wifi that other people can use) then anyone else there can see everything you do/read/say online, or even log in to a site as you, unless you are using SSL. It used to be considered low-risk because it was somewhat difficult and had to be a targeted attack, but with the proliferation of simple tools like Firesheep now almost anyone can spy on the browsing of people around them.
In short, yes, SSL, please!