When I first started blogging, I only pinged weblogs.com only, but since using Pingomatic, I find it more effective in bringing in the clicks. If you use Blogger, you can only ping weblogs.com automatically that means you have to manually do the pingomatic part. You can work around this however. Use w.bloggar. It’s a desktop post and publish utility and the new version allows you to ping pingomatic each time you post so you save a bit of work ;-).