It seems like WEP has gone the way of the dodo. According to this paper it is now possible to crack 104-bit WEP in under a minute. Here’s a synopsis.
We were able to extend Klein’s attack and optimize it for usage against WEP. Using our version, it is possible to recover a 104 bit WEP key with probability 50% using just 40,000 captured packets. For 60,000 available data packets, the success probability is about 80% and for 85,000 data packets about 95%. Using active techniques like deauth and ARP re-injection, 40,000 packets can be captured in less than one minute under good condition. The actual computation takes about 3 seconds and 3 MB main memory on a Pentium-M 1.7 GHz and can additionally be optimized for devices with slower CPUs. The same attack can be used for 40 bit keys too with an even higher success probability.
Bottom line, WEP is probably still adequate as a deterrent to casual users, but should not be used to secure wireless networks. Use TKIP (as known as WPA1) and CCMP (also known as WPA2) instead.