The Internet is a blossoming format for ESL resources. Many websites offer ESL teaching materials both for free and for a price. In addition, multiple ESL web forums allow teachers to share and discuss material. The advantage of using the Internet to collect resources for your ESL class is that you can find material of almost any type, from readings to vocabulary lists. However, the Internet provides material of limited length, meaning you will have to find resources frequently if you plan to use the Internet as your exclusive source of resources. Two examples of ESL resource websites are UsingEnglish.com and TEFL-Magic.com (see Resources).
The material that teachers of native English speakers use to teach students language arts can also be appropriate for ESL classes. This includes written dialogue, which can give students a better understanding of natural English speech, and poetry, which can help students improve their rhythm of speech. Of course, you will have to take your students' level into account; try to determine your students' level in reference to that of grade-school students. If you find that your students' English capabilities are on par with American 8th graders, for example, you can use 8th grade English texts, readings and tests as teaching resources for your ESL class.
Other teachers of ESL can offer you their resources as well. One benefit of using fellow ESL teachers as a resource is that if you seek out experienced ESL teachers, these teachers can inform you what material works best. These ESL teachers likely also have lesson plans they can give you -- something hard to find from other sources.
There are many textbooks written specifically for teaching ESL students. These texts tend to include vocabulary, readings, grammar points and speaking patterns. Moreover, many texts include CDs that can be used for listening practice. One gain that comes from using a text is the ability to follow it for a single course. This allows for simple class planning and lesson plan design. Two example texts for ESL learners are "Advanced English Grammar for ESL Learners," by Mark Lester and "English Verbs & Essentials of Grammar for ESL Learners," by Ed Swick.