The Problem: In your living room, your wireless connection is fine. Move into another room and the signal becomes weak or nonexistent.
Quick Fix: There are several things that could cause a wireless signal to drop. The big culprit is interference. Cordless phones and any device using the 2.4GHz band could be the cause. Even things you wouldn't imagine can cause interference, including mirrors and glass.
Once you've checked for physical interference, test something: Do all your devices and computers lose signal at the same location, or just one in particular? If all, chances are the problem lies with the router. Consider an external antenna for the router (if the router supports the addition). Also check for router-firmware updates. You may have to consider investing in a wireless extender.
If one specific machine is dropping the signal, update the firmware for that machine's wireless client adapter, or upgrade to a new adapter.