Bitcoin as subscription method I am contemplating designing some minor sites that uses bitcoins, but as far as I can see, a manual action is needed for every payment.

Is it possible to set up a "subscription" system or repeating transactions?

If not, I am planning to design a system where you can replenish your subscription, by simply "filling up" your account and then over time the allocated coins will be depleted.
Repeated transactions using Bitcoins is impossible, unless you have access to the private key. This requires a specific client. Such functionality is not yet available, as most people encrypt their wallets (the client can't decode it without the user. The second approach would be preferable.