I've set up a form/spreadsheet combo for Indie Authors to be able to submit information about newsletter promotions that they run. It's simple to use and gives everyone transparency into results, and what's more is people can post anonymous results to the list to help other people.
Just follow the link and you can view or add results directly to the spreadsheet simply, and I'll do my best to keep it up to date and help parse through results. Once more people have added in results and we have some actual statistics we can start parsing the data and make use of it!
So, go for it! Start adding in your results and letting other indie authors know how well different promotional sites perform. I'll be evaluating the results and posting to let people know how each site is doing.
Thanks, everyone! Hopefully, I'll be able to expand this tool down the road and make it more powerful and together we can get some insight into what promotional sites are worth your money!