hmm, if you have any inside jokes from your aim conversations, get him something that relates to it. Like, say you have a joke about an elephant, or his favorite band. Something random involving one of your jokes like the cd or a poster, or a toy elephant. If it's something unconventional and funny it will put him at ease and make him not to uncomfortable. It'll show you remember the conversations and want to be friends at school too without putting pressure on him. He'll appreciate you remembering his birthday and what you talked about.