AIM Secrets and Tricks
Let's note that these secrets and tips are AOL Instant Messenger based, and not third party client based. Including Pidgin, Trillian, web-based clients, etc etc. Only official America Online based AIM clients. Kay, thank you.

Talk To a Buddy While Offline
This can be achieved by using the option of Direct Connecting. Simply direct connect with a user, and sign off of AIM, but do not close the IM window in which the direct connection is open. When your screenname is signed off, type in the IM, and you'll notice the AIM user being able to recieve your messages.

Change your AIM Login Image
This allows you to edit the AOL Instant Messenger sign on image. If you're unsure what I mean, the image bordered in red is the AIM login image.

To find out how to do this, click here.
AIM Secret Brought To You By AIMChange.com

Send Message in Direct Connection While Sending Image
Well, when you're sending an image or file through an AIM direct connection, you are unable to send your message afterward, till the image or file is finished sending. But, what you can do, is open up a new IM window, type the user's screenname that you're sending an image or file to, and add a symbol to the beginning or end of the screenname. So say i'm sending Arielle (Im Amazing is her screenname), a file. I would type (in the new IM window), 'imamazing*', and it'll be able to send the messages. Note that when ImAmazing respondes, you wouldn't recieve her IMs in the new IM window, but the window where you're direct connected to her.
Thanks to Arielle (ImAmazing) for helping me test this secret