Colby College is a college in Maine. Prof. Barbara Nelson teaches Spanish and for over 10 years she has been sharing self-correcting grammar exercises and culture activities online, for students to practice the concepts they're learning in class.
My favorites are the song "Ojalá que llueva café" and the beautiful images for the Día de los Muertos activity. On the right-hand column, the grammar activities are listed by topic. When you complete an activity and submit it, you get feedback about your answers right away.
With Quia and Pearson's My Spanish Lab, many college classes have their workbook lab manuals available to students online, with auto-correct options for many activities. But Professor Nelson was one of the pioneers, and her simple activities are still some of the best drills available.
This website also provides instructions for making accent marks and setting up your computer with "international" keyboard settings. Click on "resources'' to locate these instructions.