thumbnail generator

Hi all, My website http://www.webentrepreneurs.ie is having a problem .
Every time i make a new post I have to manually change the url of the image to 70×70 for rs bottom and add it in as an extra.
Is there a way I can generate thumbnails from my post without going to all that extra work.
I have also set it to take rss feeds from other websites but it still will not give any thumbnails for the homepage into text, any ideas would be great, many thanks hope to hear something back