I have just created my own widget for one of my blogs Authentic Greek Recipes - you can see it near the bottom of the left sidebar. This contains the recent posts, along with photos from the blog, and I created it really easily at Widgetbox.
I have placed it on each of my blogs to help bring more traffic to Authentic Greek Recipes. The good thing at Widgetbox is that you can also make your widget a Facebook application, and then invite friends on Facebook. Once you have at least 5 who accept, you can register it in the Facebook Application Directory.
Widgetbox also has its own network, with various Channels, or categories. I have joined the Food group, and this can increase your traffic in 2 ways. Through visitors to the Network Channel itself and also, each member has a Channel widget on their blog with yours on it, so visitors to all these blogs can visit yours from there.