Frankly I don’t use Skype much anymore, and now use SIP for most VOIP calls, but I wrote previously about a hack that allows you to run multiple Skype accounts simultaneously. It wasn’t great but it worked.
There is now, at least for Windows, a slightly more elegant solution to running more than one Skype account simultaneously that doesn’t involve creating multiple Windows logins. It’s free and you can download the Skype Launcher software here. It still opens up two Skype windows but the whole process is pretty painless and now supports auto-login too.