The incredibly popular AIM/Y!/MSN/gTalk/ICQ/Jabber chat web app Meebo is now sporting an iPhone-enhanced interface. Just visit Meebo on your iPhone to start using it. Since Apple's iPhone doesn't (yet) ship with an iChat-like application, instant messaging mavens have had to rely on third-party web apps and services such as Flick IM and IM+ for Skype to satisfy their needs. Speaking of chat, have you seen the iPhone two-way video conferencing hack? Pretty nifty stuff.
Other companies jumping on the iPhone-friendly bandwagon include Facebook, Media Temple, Digg, Box.net (review), Blue Flavor and a million more.