This turns out to be ridiculously easy to do in a Skype group chat. An administrator for the chat simply has to type in the chat window:
/set options +HISTORY_DISCLOSED
After this, anyone joining the chat will see recent history. Per Skype's FAQ on chat commands:
Joiners can see the conversation that took place before they joined. The limit that they can see is either 400 messages or two weeks of time, depending on which is reached first.
I've enabled this setting on a number of chats for which I am an admin, and it's definitely helped newcomers come up to speed on what is being discussed in the chat. (Of course, some of those chats are very busy and so 400 messages may only take you back a very short period of time.)
Note, again, that you must be an administrator of a Skype chat for this command to actually execute. You can type it if you are just a user in the chat, and Skype won't tell you that it didn't execute... but it won't. You have to be an admin.
BROKEN IN SKYPE 5.1?
Now, having said all this, I recently had two people join a Skype chat and not get any history upon joining. In asking what Skype version they were using, it turned out both were running the new Skype 5.1 on Windows. Did this chat history feature get broken in Skype 5.1? I don't know... and given that I have no Windows machines around to test, I can't tell you for sure.... but I thought I'd mention it in case you have people joining a chat and not getting any history. You may want to find out what version of Skype they are using.
P.S. Note that this is VERY different from the "/history" command in the IRC-style commands for Skype I recently wrote about. The "/history" command loads the chat history ON YOUR COMPUTER into the window for the chat. However, this history is only available for the time that you have been in the chat. You are NOT able to get the history of the chat before you joined. The only way to get that previous history automatically is if an admin set the option described in this post before you joined the chat. Once you are in a chat, the only real way to get chat history is to ask someone else to copy/paste their history either directly to you or in the chat itself.
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