Mobile device software maker Softcentral has released a public beta of its Yak On! Instant Messenger for the BlackBerry.
Yak On! provides AIM and MSN instant messaging for the BlackBerry and allows you to stay logged to both AIM and MSN simultaneously while working with other applications in the foreground and uses direct connections from your service provider to the AIM and MSN instant messaging servers.
Yak On! can be used on color BlackBerry devices and you can get full list of all the feature by taking a look at the user guide.