A.M.
hi there! what i've been using is local college career services and posting online exactly what i'm looking for (experience with toddlers, infant/child cpr, no smoking, etc.). i don't know if any colleges are nearby, but i was lucky in that we are close to BU and BC. my daughter has fantastic sitters at great rates!
other than that, i've heard good things about sittercity.
good luck!