To my knowledge, there is no such service. Rescanning the blockchain from scratch takes a good bit of server resources, and is definitely not a few simple lookups.
However, I can think of a way, but one which is discouraged (and I don't feel too bad mentioning it here, since it's a paying service).
Generate a view only wallet using the donation address and view key with simplewallet. Run
seed to get the matching seed. Import that seed into MyMonero, and pay the 10 monero fee. Wait a bit for donations to show up.
You won't see spends though, since you do not have the spend key. Also, note that incoming outputs may be either donations, or change from a transaction spent by the donation address, so you won't see the total donated unless that wallet never spent anything.