Ohhhhh I know how you feel ... and it is just one of life's little heartbreaks we just have to deal with. Hope you will be able to take some short visits - but CALL FIRST! Just taking them out to lunch/dinner once in awhile is a big boost.
One thing my son did was set up my computer with Instant Messaging. I just loved it when I would be online and all of a sudden a message popped up, "Hi, Mom" Of course now there is Text messaging.
And don't be down if he doesn't come home every weekend. They have so many activities for Freshmen particularly, and it's all a part of college life. And when he does come home, be sure to fix all his favorite things :)
Good Luck....I know how hard it is...but it DOES get easier. (My DD went away to college the very next year, and it wasn't nearly as hard on me)