I am planning on starting an intense marketing campaign, with one of the methods involving sidebar ads, and I was wondering how people go about creating those? Where can you find images that you can use for free?
Are you talking about the "your ad here" ads? I had mine set up as a HTML/Javascript widget in my sidebar with images I uploaded and linked to. Then I switched to Project Wonderful, but you won't make much money with them unless you have A LOT of traffic. I also have affiliate ads in my sidebar as well. I wish I had the traffic and PageRank to do private ad sales. It's a good way to make 10 bucks or more an ad if you have a decent site. I can help you with some generic placeholders in Photoshop...free of charge. PM me if you want some help. Best of luck.
Oh...so you want to create like a 125x125 ad and buy advertising on various sites? You can get free stock images at http://sxc.hu Hope this helps.
I use ulead gif animater to create all my banners. You can get the images of loads of sites on the net http://www.sxc.hu/ does look like a good site though, so you will probably find the images you want there.