This is a list of my favourite services and websites I personally use and pay for. I share only information that I think is valuable.
If you are going to sign up for some of it, please use my links so that I can get credit for referring you.

My choice number one when I need to study a new field. Until today I paid for exactly 40 courses about all sorts of topics.
If you are starting with Prestashop, I recommend you this one:

Learn How To Build An E-Commerce Web Site By Prestashop
Learn How To Develop and Manage an eCommerce By Using Prestashop platform To Provides A Professional Web Store

Some of my other favourite courses (not related with Prestashop):

- How to Learn and Memorize the Vocabulary of Any Language
- Amazon Store Management: Run a Successful Amazon Store
- Evernote for busy professionals

Running an eshop often requires to use some pretty images - maybe for your "Homeslider" module or for your newsletters.
I prefer to get stock photos from because I found the ratio between quality and price to be the most reasonable. A typical picture (around 1300x800px) costs me normally around $8. But of course, that also depends how much money you transfer to your Fotolia account (the more, the cheaper the photos will cost). In my case I calculated the price with only $50 deposit.

In case you are searching for some specific Prestashop module, I suggest Prestashop category on as an alternative to Prestashop Addons.

This can be a great source of inspiration for the design of your theme, I used GraphicRiver also a couple of times when I was searching for a logo.