The best Wi-Fi extender is currently the Linksys RE6500, according to TomsGuide.com. It is a small, inexpensive device that is easy to set up and excels at extending the range of a Wi-Fi router's signal.
With over 150 five-star ratings at Amazon.com, the Linksys RE6500 extends the range of any Wi-Fi signal by up to 145 feet and has four LAN and audio ports. It supports the 2.4 and 5 GHz wireless bands and also has two removable 3 dBi dipole antennas. It has received an 8 out of 10 rating at TrustedReviews.com, and the only drawback listed is the lack of a USB port.