I was already using graphics programs, primarily Skitch, to make my text to image pins offline and loading them manually to Pinterest, but that involves a lot of steps. There are a lot of web apps for generating social media text to images but they're often unnecessarily complicated and often not free. I finally found one (and a half) apps that I like.
As long as you don't need fancy backgrounds or extensive annotations, I recommend Quozio
http://quozio.com/bookmarklet/. You highlight your text, click a bookmarklet or enter the text manually and Quozio generates an image with social media buttons. It's free, web-based, doesn't require an account or installation of anything. The only problem is that Quozio picks a random style (which you can change after the fact) that isn't always easy to read and Quozio's style menu itself changes randomly, so your favorite isn't easy to find. I wrote my own bookmarklet to force Quozio to reload the image in its easy to read white on black style. So after the Quozio bookmarklet has done its thing, I click my own bookmarklet and then I pin.
The javascript for my bookmarklet is
javascript: (function(){var url = window.location.href; var newUrl = url.replace(/=[0-9]*/g, "=1005"); document.location.href = newUrl;document.location.reload();})();
(If you like a different style you can substitute its number for the "1005")
Make a bookmark that goes on your bookmarks
toolbar, put in the code exactly as written above (all one line) in the location section for your new bookmarklet. EDIT: Wow, learn something every day - to make a bookmarklet, you can just grab the italicized text above and drag it to your bookmarks toolbar. Then rename it.
Alternatively you can memorize your favorite style (labeled t=xxxx at the end of the url) and append it, then force refresh the page. So if the url of your image was
http: //quozio.com/quote/ef4c6b0e#!t=1006, but my favorite style is t=1005, I change the url to
http: //quozio.com/quote/ef4c6b0e#!t=1006&t=1005 then force refresh (simply hitting enter once the new url is in place doesn't work - you have to do a force refresh - usually command-R or something similar).