I've just managed to successfully compile and install the microblog-purple Pidgin plugin on OpenSolaris (so I can use Twitter and Identi.ca from Pidgin). Sadly, the installation wasn't the prettiest of things, but the important part is the new protocol library files compiled successfully and work a treat.

For the curious, it was a simple matter of following the instructions:

1 $ wget https://microblog-purple.googlecode.com/files/mbpurple-0.2.4.tar.gz
2 $ gunzip -cd mbpurple-0.2.4.tar.gz | tar xf -
3 $ cd mbpurple-0.2.4
4 $ export PATH=/usr/gnu/bin:$PATH
5 $ make
6 $ pfexec make install

Notes about some of the lines are needed.

1-3: self explanatory
4: this is to ensure the GNU tools are first in my path. microblog-purple has been configured to use commands as they appear on Linux, not Solaris. By pushing our GNU tools to the front of our path, we ensure we don't hit any problems.
5: this compiles without any problems, though you may get "cc: unrecognized option `-pthread'" warnings. These can be ignored, but if you don't want to, you can change the global.mak file and just append "s" to this option, thus "-pthread" becomes "-pthreads" wherever it occurs.
6: This will produce loads of errors, however the actual libraries are put in place successfully.

If you want to install this plugin into your ${HOME}/.purple/plugins/ directory instead, replace step 6 with the following commands:

$ cp microblog/lib*.png ${HOME}/.purple/plugins/
$ cp twitgin/twitgin.so ${HOME}/.purple/plugins/
$ cp certs/*.pem ${HOME}/.purple/certificates/

And that's it. You shouldn't even need to restart Pidgin. You can now add TwitterIM and Identi.ca (or Laconica) accounts via the usual "Add Account" interface.

Whilst we're on the topic of Twitter and Identi.ca, you can follow me at https://twitter.com/lildude and https://identi.ca/lildude respectively. Note, I'm more active on Identi.ca than Twitter.