Light and simple Skype Button plugin (w/ Official or your Skype Status Icons) in post/page/widget or floating. Skype Status updates without refresh.
You can use your own images to represent Skype Online Status and it refresh it automatically without reloading the page. v2: All skype buttons in one (shows the first online account found), ability to change skype button action (call, chat etc.) by changing your status and status in plain text.
See question above AND it's much more lightweight, other plugins I found were full of stuff that (I think) nobody would use and it just slows down your website for such a small thing like Skype button.
Make sure you set your skype status visible on the web in your Skype settings (Menu: Skype -> Privacy...) the option "Allow my skype online status to be shown on the web"