If you want it secure from people that have access to your bot('s computer): store only the $md5 of your password as Iori said.
If you want to protect against people sniffing your connection: store your password normally on your bot, and when you want to login, first let your bot send a large random number and your $address, then send as password $md5($+(given address,given random number,password)). Also, allow only 1 login try per random number, limit the sending of random numbers per host (maybe reset it after successful login) and set a limited time for logging in. (1 or 2 minutes?)
Protecting against people that can read your bot's files AND sniff your connection: I don't think it's possible

Oh yeah, if you're on someone elses comp: don't use // to have it parse the $md5, use <tab> to parse it immediately and to keep your password out of the editbox buffer

(The same line cannot be used later, because you've already used that random number, and the chance of getting it again should be negligable)