If you're using Windows Live Messenger, you'll know that it'll automatically stores your chat history in your computer so that you can access them anytime you want and find out what you've said a few weeks ago. That sounds quite useful but here's a better tool.
IM History is a desktop app that helps users store their chat history online and allows them to view and access them online on their Web browsers using a one-click access from their PCs. Currently, IM History supports multiple IMs such as AIM, Skype, Windows Live Messenger, Yahoo Messenger, ICQ, Pidgin, Miranda, Trillian, QIP, etc.
Before you IM History records your chat logs, you can upload and merge existing history archives. The impressive search feature enables you to search for chat logs by bookmarks and links, word/phrase or by contact. You can even create a metacontact for your multi-IM chat buddies or edit the contact details.
