We need these to build it

apt-get install gettext libglib2.0-dev libgtk2.0-dev libxml2-dev

perl-xml libraries may also be needed

apt-get install libxml-perl

To build it with ssl (needed for msn and google talk), we need the gnutls development headers

apt-get install libgnutls-dev

Get the source

http://superb-east.dl.sourceforge.net/sourceforge/pidgin/pidgin-2.3.1.tar.bz2

Build it

tar jxvf pidgin-2.3.1.tar.bz2
cd pidgin-2.3.1
./configure --enable-gnutls=yes
make
make install

pidgin is at /usr/local/bin/pidgin