I recently came across a useful little app that lets you save your IM chat history online. IM-History is a free tool that resides on the system traybar and uploads all IM chat history to one secure website, which can be later accessed from anywhere in the world. It is a small yet powerful tool, that takes very less system resources while running seamlessly in the background.
It currently supports Windows Live, Yahoo, Skype, AIM, ICQ, Trillian, Pidgin, Miranda, and QIP 2005 Messengers only. Once you run the program, it will ask you to sign up, that will take a few seconds if you are fast. Once you have confirmed your email address click Proceed. It will begin detecting all Instant Messengers installed on your system and you can then choose which IM chat history do you want to save, you can select all if you want to save all chat history(see screenshot below).
Screenshot taken from official website.
In my test it failed to detect Windows Live Messenger 2009, I believe it supports Live Messenger 8.1 and older versions only. You will have to restart your messenger once you have selected it to save chat history.
You can view all your chat history on the website or inside this easy-to-use tool anytime and anywhere you want. It is available for both Windows and Linux. Enjoy!