This portal offers short "language trips" about different topics. Each lesson deals with a different subject and includes different exercises. On the right side of the page, you can find a sidebar with a exercises for general grammar topics in Spanish.

This learning site provides grammar exercises for beginners to advanced Spanish learners. The site is clearly structured and easy to use.

This site publishes grammar articles by topic. Perfect if you are looking to practise Spanish grammar by reading articles about grammar topics instead of reading traditional grammar lessons based around one topic.

Languageguide.org provides a comprehensive introduction to the basics of Spanish grammar. With many examples and audio recordings.

Under the playlists "Spanish I/II Videos" and "Spanish III Lessons" you can find numerous excellent videos that explain grammar topics in a simple and straightforward manner.