i too don't have any idea for .ly
I think if you have one char domain, then keep it for 3-4 years even on 150$ a year and you can generate fortune with these.
One letter domain is always worth to keep hold. I don't see any future with a .ly except if you develop it though. As you have already bought it atleast make a 5 min WP blog on it.
Who knows if there is a company with a MLY name on it interested.