My Top Favorites:

These are sites that I go back to over and over again!

English Page

https://www.englishpage.com/verbpage/verbtenseintro.html

My very favorite.  It has great explanations, with really good verb tense contrast exercises.

Study Zone

https://web2.uvcs.uvic.ca/courses/elc/studyzone/grammar.htm

You'll need to navigate into "Verbs" and then "Tenses", but this is another site with not only explanations and exercises, but good verb tense contrasts.

Perfect English Grammar

https://www.perfect-english-grammar.com/verb-tenses.html

This site has three different pages for each tense: making, using and practicing.  It also has some nice tense contrast explanations and exercises.

My English Pages

https://www.myenglishpages.com/site_php_files/grammar.php

Very wide variety of grammar topics with brief explanations and an exercise to an exercise for each.

ESL Lounge

https://www.esl-lounge.com/student/grammar-exercises.php

This site is divided into five levels, from beginner to advanced.  Once you find the topic you need, there are nice, concise explanations with embedded quizzes.

More Great Resources

Tes

English Grammar with Jennifer

https://www.youtube.com/playlist?list=PLEEA0D5FA42DB4C58

Many of you know Jennifer from her pronunciation site, but she has some very gentle, well-explained grammar videos as well.

Fraze-It

https://fraze.it/n_search.jsp?spell=1&t=2&l=0&q=fly#q=fly%20%2Ff%3Ae%20%2Ft%3Apap&findid=-1&ff=&ffo=true&l=0&t=0

This is an interesting site in which you can type a verb, then choose the tense you'd like to have exemplified, and it will give you real results pulled from news sites all across the web.  You can even edit the results within a topic, i.e. business, food, education.

Test English

https://www.test-english.com/grammar-points/contents/

Lots of good exercises here; when you first choose a topic, you're directed to the quiz and then can choose another tab for "Explanation".  Be aware that it tends to be more British!

ESL Tower

http://www.esltower.com/grammarteachers.html

This link is the same as above, but printable grammar worksheets oriented to teachers--a wide variety of subjects.

Learn English Feel Good

http://www.learnenglishfeelgood.com/esl-english-grammar-exercises.html

OnlinePrintable

This website may not have explanations, but such a wealth of exercises--great for when your students need extra practice--great upper level resource!

http://www.learnenglishfeelgood.com/esl-printables-worksheets.html

English 4 U

http://www.english-4u.de/grammar_exercises.htm

Many, many online exercises, graded in easy, medium or difficult.

English Hilfen

https://www.englisch-hilfen.de/en/exercises_list/zeitformen.htm

Lots of links to verb tenses, with contrasts.  For the explanations, visit another page: https://www.englisch-hilfen.de/en/grammar_list/zeitformen.htm

ESL Blues Trivia Grammar quizzes

http://espace.cegepmontpetit.ca/prof/epritchard/doubleql.htm

This is a fun set of trivia quizzes based on different verb tenses and voices