The Apple Airport Express, back when it was a cube you plugged into the wall, made for a great portable router you could take anywhere and set up easily. Then it changed to a hockey puck that requires a cable. The TP-Link Wireless N150 fills the pocketable router void and for a quarter of the price, too.
For around $25, you get a pocket router that supports 802.11b/g/n wireless through one little Ethernet port at the bottom. While you save $US75 over Apple's version, you do sacrifice a USB port and audio jack. It isn't quite as feature-rich as the AirPort Express, but if you need a router you can take with you and you don't want to spend a lot, this will solve your problem.
TP-Link Wireless N150 Mini Pocket Router (~$25) [Static Ice]