DesignsbyJUJU.com is having a sale on fonts. You can buy them as a set or 12 sets for $12.

There are many free fonts available too, most you need to sign up for a newsletter and each day log into the site to download the next letter.  Each digitiser has their own system, with some sending a link via email. 

Some digitisers offer lower case, numbers and punctuation as a separate purchase but check before purchasing because sometimes you'll find the lower case etc might suit several upper case freebies. 
Do a Google search and you will be inundated. 

Hope this helps?

As mentioned already, there's lots of fonts out there for just a few dollars.  One thing I discovered, to be careful when purchasing a font, is that it includes numbers and punctuation symbols!  I had bought a "Honey" font and sat down to embroider a table scarf with a wedding date on it, only to discover missing punctuation (if someone knows if this is incorrect please feel free to LMK where it is...thanks).

I have 15K with built-in fonts.  It was mentioned in a previous post that there are other fonts available.  Where can I find them?
Thank you,
Carole