I've only knit a few pair of socks but my favorite for both softness and quality is Lornas Laces. They have a new Green Line...but I haven't seen it locally. One skein of their yarn is rather speedy but you could probably get quite a few baby socks out of one skein or make a matching hat.
You might also look at Blue Moon Fiber Arts, socks that rock yarn.. they are on line. They are very popular too, though I haven't used it myself.