Sure. Well I'm using Electrum and it's possible to add a description to your payment. Will have to check if that's standard.
Eventually jga's module is what I need, because it's the only way to automate things. For small scale I think it can be done my way as well..
I have not tried Electrum yet, just having a look at it now and it seems quite impressive. My plan is to just dump all the BTC into an offline wallet each day/week.
From the standard bitcoin-qt client, I just had a look and it does not look like you can add a comment when sending a payment, only a label for yourself. Maybe I am missing something.