Here are two tools that you can download and will allow you to post updates to your Twitter and Facebook feeds.
Tweetdeck is a nice tool that allows you to see your various tweets, posts, what people you follow are tweeting or posting, etc.
Seesmic – advantage over Tweetdeck is that it allows you to manage multiple accounts, so you can Tweet for your special events and have a separate one for your advocacy if you like – and you’ll be able to manage them both with the same tool
Both of these tools are built using the AdobeAir platform. You will be prompted to download AdobeAir if you don’t already have it. It’s a fairly small download.
Please test out both and see which one is more useful to you.