I was just reading this article, and there are tons of links with great lunch ideas in it! I'm definitely planning on trying some this week for work :)
I usually have some kind of salad with chicken (or chicken salad sandwich), as well as some fruit and yogurt, which has lots of fiber (to stay full). I don't get off work until after 6, so I understand having to wait to eat. If it is at all possible to eat while working, I would suggest doing so. I tend to get hungry in the afternoons, and by bringing the fruit and yogurt, I can snack while still eating healthy. I like snacking on raw carrots as well. For me, the longer I take to eat, the less hungry I feel later (guess I'm tricking my brain). Anyways, hope this helps.