One friend, who was a usual guest at my dinner table, always brought either flowers or wine. It was particularly nice when he brought flowers because they were something I considered an indulgence. My roommate and I would drop them in the closest vase, or something vaguely resembling a vase, and the table was set. Another nice touch is something that Alysson often does. Buy flowers from the grocer and dress them up in nice paper. (Even newspaper can look good when tied with a pretty bow.)
Wine is a welcome treat, too, even if it is not intended to be consumed that evening. I've received many a bottle of my favorite wine or port when the table was already full of libations. The gift can be saved for another occasion. The next dinner party they invite you to perhaps.
So why bring anything? Consider the fact that your host/friend has gone out of their way to accommodate you. Even the tidiest of hosts must spend some time freshening up their place. I should know, since I always devote a few hours to cleaning before a dinner party. Meal preparation also requires substantial time (not to mention money) to ensure a scrumptious feast. And don't forget the fun afterwards. While you are crawling into your cozy bed, your host is cleaning up the equivalent of a week's worth of dirty dishes. I'm lucky enough to have friends who linger around for the dishwashing, but I never expect it.
I used to throw dinners on a regular basis, but the cost and time made the experience less than enjoyable. Downsizing and limiting my feasts to simple, managable meals (my boyfriend gets the experimental dishes), has made dinners with friends a reality once again. It would seem that throwing a dinner for friends is a burden, and for some people it is. It also explains why places like Applebees and TGIFs are still in business. If you haven't had friends over in while, invite them over. For me, it feels good to wait on other people, but home is also an intimate place for people to get to know you better.
***For an easy gathering with friends, consider brunch. Many of the dishes can be made a day ahead of time so that you can enjoy your friends' company. Also, you can serve a signature drink like Bloody Marys or Mimosas, or be adventurous and invent your own breakfast concoction. With clean up at a minimum, you'll have the afternoon to take a nap!