Barbara Befani, a reliable source of high quality information, has held a talk at the Centre for Development Impact on choosing appropriate evaluation methods. Listen to her presentation here; it comes with a slide show that is best watched while listening to the talk.
The spreadsheet which helps choosing appropriate evaluation tools is available from the BOND website here. Enjoy! And contain your disappointment if you realise that most methods won't work with the weak data and skimpy resources available for your evaluation.