I tried the Earthlink/Boingo software but the interface is just plain ugly and the program seems really simple (in Earthlink's defense, it is aimed at getting users on to its paid network - it just hapens to also find free ones).
Right now I'm using PCTEL's roaming client, which has a great looking interface but is not free. Also, whenever my connection speed drops, it identifies the network as 802.11b rather than g, and it says the encryption is "unknown;" it is WEP. Minor annoyances; overall it is pretty nice.
But I'm wondering - anything else out there to try for finding and connecting to multiple wireless nets?