Ok, bit redundant. But since Facebook chat was removed recently from / doesn’t work on facebook.com, on iPad, here are some free IM apps / alternatives:

eBuddy (iPhone app) with notifications for up to 1/2h
fring … i’ve used this app on iPhone & the newest version does not log you out automatically, but the interface … confusing
– TwittDeck – you can actually plug in your FB on it ? – nope, only on iPhone version
FB iPhone app has chat on it