Fring
I have been using fring - chat and VoIP telephony - on my N80 for a few weeks now and I really think this application rocks. Note: I have only used fring for chat - no calls yet.
This week, fring announced support of MSN (Skype and GoogleTalk are already supported). I tried it today and it works really nice. Apparently, fring is able to add services dynamically because I did not update to a new version - the MSN service was just added when I opened the application today. That is really clever!
Fring used to have some problems running on N80 (see fring forums) - the first version I tried (2.71) would freeze when loading, but a recent update to v.2.74 has fixed that.
Here is a nice review of fring with some screenshots (made before the MSN service was added).
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