What To Look For
The AOL email system has been hacked and multiple accounts have been compromised. These compromised accounts are sending emails with malicious links to other AOL account holders, as well as people who have email accounts with other providers. To see if your account had been compromised, check your sent folder to see if there are any emails that you did not send in it--if there are, your account is likely compromised.
How to Protect Yourself
Even if your account doesn't seem to be compromised, it's best to reset your password just in case. If you do think your account has been compromised, reset your password immediately and make sure your computer is running an updated anti-virus software. AOL has outlined the complete list of steps you should take to correct the problem here: http://help.aol.com/help/microsites/microsite.do?cmd=displayKC&docType=kc&externalId=51598