Language Guide
Language Guide: El Participio Pasado
This grammar tutorial explains the formation of the past participle for ar/er/ir verbs as well as some irregular forms. A couple of examples are given to show the formation of the present perfect.
University of Texas at Austin
University of Texas: Francais Interactif
This full-featured interactive textbook encounter utilizes French speakers in real life scenarios. Well structured for work on grammatical concepts (links to Tex's French Grammar), vocabulary, listening comprehension and exposure to...
Other
Kryss Tal: Grammar: Introduction to Grammar
This site provides a very good overview of grammar components. Grammar examples and links are provided.