Teaching the use of articles to a low intermediate group of ESL students can be tedious, especially if it's focused on lots of repetitious exercises, choosing between "a" or "an," zero article, or "the." My students in a grammar seminar were fairly competent at understanding when to use "a" or "an" with a countable noun beginning with a vowel sound and understood that "the" has to be used with certain proper nouns, such as rivers, mountain ranges, and islands. The hard part of using articles was deciding when to use them within larger structures than a sentence.
For that, an engaging and challenging activity for lower level English language learners is trying to put missing articles into a short paragraph. For this activity, I used paragraphs from an online site called News In Levels. This great site summarizes random news of the day in one paragraph. It has four levels for ESL students from Level 0 to Level 3. In addition, a few key words from the target paragraph are highlighted and defined, and there is a cloud-based audio recording of the paragraph.
To illustrate one way that you can use these paragraphs for teaching use of articles, you can view and/or download a copy of an exercise I did in class. Later, I used the same cloze activity to quiz my students.
For some thought-provoking generalizations about grammar instruction, you can also have a look at Diane Larsen-Freeman's digest.
***I checked the online link to News In Levels which began in 2011. It states that the site was begun as a school project and was meant to last for 1000 days. The producers of the materials are requesting donations to keep it going. It is currently free. If you like the paragraph samples, then I suggest downloading some before they disappear or making a small online donation to see if we can keep it going.