I like Julien Vermillard's logos the most. Esp 5 with the twin color yellow-green rings. I'd like to point out a couple of things. IMO MINA should not be written in sentence case. It should either be all caps or all lower case.
At the same time, the logo should be in multiple formats - just independent logo, logo with tag line, etc. The tag line also needs to be finalized if it is not yet done. "Easy network programming", "Network app framework", etc etc. If the acronyms NIO / IO could be included somehow in the tag line, it would make MINA much easier to find in searches. Regards, Vinod.
