Factcheck.org has sifted through the mixed barrage of messages that both major presidential campaigns have been sending, and has cleared up many of the mistaken or deliberate misinformation being spread. Both campaigns are lying to some degree.
McCain criticized Obama of "spreading the wealth" when he has supported similar progressive tax reform. He also labeled Obama's tax refunds as "welfare," even though his health care plan also uses tax credits. Obama's tax credits require employment.
Obama's campaign has distorted the facts about how much McCain plans to cut from Medicare and Medicaid to cover health care. They also lied about McCain's stance on stem cell research. He was against it before 2001, but is for it now. More at source.