We already know cool and clever way to download files while at work in office. There are similar web ways to access instant messenger in office without any need to download any software. You can try any of multi IM supported web based messengers.
Meebo rules the list but since its so popular – it will be most likely blocked in your office. WeBuzz.im is a new web based messenger service. Since this web service is new, you can use it till your office IT guys get sniff of things.
Using this, you can connect to Gmail, Yahoo, Live/Msn and AIM instant messengers. Checkout WeBuzz to keep you buzzing on your favorite IM – be careful, the boss is around! [Access blocked websites with WebinMail]