So, now you know how your site performs, what do you do about it? Here is a collection of resources ranging from self-help to commercial solutions that can help you improve the performance of your site (usually quite significantly).
Disclaimer: the commercial services and consultants listed here have all contributed to WebPagetest in some way (usually by running a test location). This isn't an exhaustive list of services available but these are certainly well-vetted experts in their areas and have been working on web performance longer than most people.
These are software, device or services that will automatically apply optimizations to your site
If you're comfortable doing the optimizations yourself or are just interested in learning more, these are great places to start