University of Victoria (Canada)
Elc Study Zone: Basic Prepositions
This site explains the various uses for "in," "on," and "at" in phrases referring to transportation, time, and communications (TV, radio, etc.). Also links to a practice exercise.
Grammarly
Grammarly Blog: Unnecessary Preposition
This page explains that changes in usage over time makes the use of prepostions in certain instances unnecessary. While they are not technically incorrect, they lead to wordiness and should not be used. Examples are provided.
Study Languages
Study Spanish: Ir a + Infinitive
Good introductory lesson to the use of "ir a" to indicate future events. A list of adverbs that denote future time periods may also prove useful. "Poder", "acabar de", and "volver a" are introduced as other double verb constructions. A...
PBS
Pbs Learning Media: How to Use Prepositional Phrases
Prepositions indicate the location of a thing to another thing across time or space. Prepositional phrases contain a preposition and its object. [0:44]
English Club
English Club: Learn English: Grammar: Preposition
Links to information about prepositions including: What is a preposition, preposition list, a simple rule for prepositions, prepositions of place, and propositions of time.