I’ve used Yamli before, although it’s been a while. Today I found out about Google Ta3reeb, which looks like it works pretty well.
This is for if you don’t have an Arabic keyboard and you wish to type in Arabic. It will convert English characters into Arabic script.
Type in ‘hada almoq3 3zeem jiddan’ will get you هذا الموقع عظيم جيدا. I think that’s pretty good.
Also, here’s a nice little post on someone else’s blog about the word “madrasa” and cultural misunderstanding.