After I got done with my Dutch course on Memrise, I just felt . . . itchy to keep learning (the site's addictive, man). So I started working on French courses. And I can tell that it is going to be great.
I have a lot more resources for French than Dutch -- not only good, fun courses (ie ones with no typing), but I own more books in French and have a bunch of movies with French dubbing and/or French sub-titles.
I have held back from French for a long time because I didn't want it to interfere with Spanish, but that I've started, I just don't feel like I can, or even should, stop the rush. I don't see too much interference so far, but the combination of being a native English speaker and knowing a goodly amount of Spanish makes it so I can already read parallel texts of French much, much more comfortably than I can in my current level of Dutch.
If do several thousand (or, I dunno 10-20,000 words) of French on Memrise and read my two parallel text books of French short stories two or three times, and watch some movies in French here and there, I can probably be at a pretty good level in French by the end of the summer.
That and my million word challenge in Spanish might make it two reading languages down and one to go when the school year starts back up.