This site offers fundamental explanation of subject-verb agreement, additional information, and examples of exceptions to the general rules. Good information at this site, but does not link to other information.

Introduces conditional verbs. Begins with discussion of real and unreal conditional verbs. Offers a table of examples and links to additional information and exercises.

This introduction to the present tense conjugation of the irregular verbs "dar", "ir" and "estar" is easy to understand and includes a short test at the end to test the student's mastery of this grammar principle.