Free basic English courses aimed at English speakers are found online at Alison.com and English-Online.org.uk. Courses that are aimed specifically at Spanish speakers are found at Curso-Ingles.com.
Alison.com provides a large range of English courses, such as basic English grammar courses, English language and literature courses, English vocabulary and punctuation courses, and English for tourism. All courses are written in English and aimed primarily at English speakers.
English-Online.org.uk offers English courses for children, beginners, elementary, intermediate and advanced learners. The basic course teaches grammar such as possessive form, personal pronouns and verbs.
Curso-Ingles.com offers a basic English course specifically for Spanish speakers. It provides lessons on nouns, adjectives, verbs and other language functions, as well as quizzes.