BBC Parts of Speech
Nice introduction to basic parts of speech, each with a video, a factsheet, a worksheet and an online quiz
Interlink Lang. Center Parts of Speech
Great introduction to the eight basic parts of speech, plus articles. Includes pop quizzes for each section.
English Grammar Word formation
Lots of word formation exercises.
ESL Lounge Word Formation
First Certificate is a British test, but this site has many word formation exercises.