I used to but I've quit entirely. Seriously, for email and searching I use google and for IM I use MSN and AIM.
I do have this Yahoo email account that I created in '97 though. I didn't use it for about six months to year and then I starting using it again for close to year. One day I get an email warning that the account was being closed due to inactivity and then one day the account wasn't there and I created a new one for the exact same name.