I really love using Seller Tools, not only for creating sales, but for the treasuries. I think those help my sales more than anything. I've been able to make one very easily and quickly. The best part is the notifications you send out after the treasury is made!
I especially like the promotion tools which has easy schedule set up with all options I need. Saving a LOT of time on a daily basis! Keyword and trend tools give information to think about and to improve the tags and titles, really helpful. And since this is dynamic, you can stay tuned to the changes in the area of your interest with no waste of time for search it in other way.