SRMM

The chat interface surely is the most important part of a chat program.

There are several solutions, based on two central plugin architectures; SRMM (Send and Recieve Messaging Module) and nConvers.

nConvers
nConvers represents a "conversation-style" type of messaging. nConvers recently came with an updated version, nConvers++, by donatas.

SRMM
SRMM is the standard messaging module supplied with Miranda. It is simple, and straight-forward, and although lacks some features, is perfect for out-of-the-box use.

tabSRMM
tabSRMM is based on SRMM, but adds tabs, and (now) a whole host of new features. Probably recommended for new users who wish to add more features to SRMM.

Scriver
Scriver is a SRMM clone with added support for IEView. It also has the ability to use tabs.

Other related plugins

 * SmileyAdd (for the SRMM-type), replaces smileys ':)' with graphical pictures.
 * IEView adds the ability to change the message log appearence using CSS/HTML and provides animated smileys.