Look for N-Wireless routers.
While B/G is accepted among most, if you're far away from the router your signal will fade a lot unless you have specialized equipment.
The N protocol has a longer range than either of its own predecessors. B and G had an effective, unobstructed range of about 100 feet. N supposedly has a range of nearly 700 feet though in practice I've not achieved anywhere near that. Most N routers also have two aerials, allowing them to transmit a dual signal, which can give much faster reception rates on appropriate network cards.
All N routers have backwards compatibility with B and G so existing network cards and laptops will work fine with them, but if you have rangeboosted and speedboosted N equipment you will see a noticeable difference.