One of many people's must-have utilities, and like competitor Fring before it, the VoIP and chat client Nimbuzz has been finally ported to make full use of the touchscreen on the Nokia 5800. In fact, not just a straight port, since the developers have produced the most Nokia-like UI of any third party app for the 5800 that I've seen so far. Screenshots and download link below.

(Grab your 5800 version of Nimbuzz by going to m.nimbuzz.com in Web on the phone
STOP PRESS: this wasn't working just now, so download from the main desktop download page)

Here I'm using it in IM mode, showing my buddies on Skype

Note the consistent use of the S60 5th UI throughout. In the right hand shot, I'm chatting with Rafe...

Oodles of settings; and it's easy to send files and images directly to Nimbuzz-connected IM friends

Showing the full list of currently supported IM communities in Nimbuzz...