Roman Forum, Palatine Hill in the background, the neighborhood of the wealthy, where Cicero lived. From wikipedia.org

Drills to accompany the Oxford Latin Course, College edition, chapter by chapter.

Sphinx, a set of drills for verb forms including some irregular verbs.

Poetic devices used in Horace's poetry.

A site for Latin pedagogy which is also the source for some of the images used as decoration is VRoma, Virtual Rome.

Other aids, created for the earlier edition: Oxford University Press' companion website for this text. They are for the older edition but you might be able to find the equivalent grammatical items. One is by me, the other is very different and worth a look.

Other exercises which might be helpful, based on the 2nd edition of the high school course (OLC ed. 2) and not the College edition. Much of the material remains the same, however.

• John Gruber-Miller's excellent collection of exercises and links to accompany OLC.
• Quia: Language exercises and various games
  Specifically for the Latin Oxford Course,
• Internet Workbook for the Oxford Latin Course, by Robert W. Cape Jr.
• Barbara McManus' drills for Oxford Latin: Volume I so far, including some practice on making nouns and adjectives of the same or different declensions agree
• Barbara McManus' aids to understanding sentence construction
• Greg Swann's study aids for Vols. I, II, and III. Several of its links are no longer available, however.
• AbleMedia's wonderful collection of aids including Latin drills but not limited to that.