The Switch Spell plugin for Pidgin is not included in the pidgin-plugin-pack package for Ubuntu Hardy 8.04. In order to spell check in multiple languages, you'll need to download, compile and install this plugin manually. Here's now to do it.

1. Install the language pack for aspell for the languages that you want to spell check. For example, Russian:

sudo apt-get install aspell-ru

2. Install some prerequisite packages.

sudo apt-get install libgtkspell-dev pidgin-dev libpurple-dev gettext build-essential

For Intrepid also install

sudo apt-get install intltool

3. Download and unpack the source code from http://plugins.guifications.org/trac/downloads

For HARDY

wget http://downloads.guifications.org/plugins//Plugin%20Pack/purple-plugin_pack-2.3.0.tar.gz
tar xfz purple-plugin_pack-2.3.0.tar.gz
cd purple-plugin_pack-2.3.0/

For INTREPID

Download the file: http://plugins.guifications.org/trac/downloads/14
tar xfz purple-plugin_pack-2.4.0.tar.gz
cd purple-plugin_pack-2.4.0/

4. Configure

./configure

5. Make and Install (In this case, I only want to install the spellswitch plugin)

make
cd switchspell
sudo make install

6. Restart Pidgin and enable the plugin (from Tools > Plugins).

You should now see a new “Spell Check” menu in your chat windows.