Windows live messenger, Yahoo Messenger, Gtalk, and so on... All of them have nothing to do against a firewall installed on your job's computer. So, do not fell disappointed and do not think that there is not solution for this problem (for some people is a complete tragedy to not have the possibility to chat with their friends). How can I be so sure about this? Ok, that is because the existence of IM, or instant messaging services (also called Instant Messengers).
The instant messaging services —most of them— work perfect even if the computer in which the are being used has a firewal installed, or some kind of anti virus which blocks the messenger software.
Fortunately, there are a lot of instant messaging services all over the Internet. For instance, you can visit www.meebo.com and then you can have conversations and also video calls. Also, www.ebuddy.com, Imo.im, www.messengerfx.com, www.aim.com, and so on, have been successful up to now. Day by day there are appearing new IM, so the dependence to messenger software is decreasing and the popularity of the instant messengers is increasing.