Sight words are words that appear frequently and cannot be sounded out using usual decoding rules, therefore readers must memorize them by sight. Many of these words are difficult to sound out with the usual decoding rules and are good ones to memorize.

A New Model for Teaching High-Frequency Words
This article categorizes high-frequency words according to spelling - either "regular" or "irregular" to make reading and spelling the words easier for all students. The rest of this Reading Rockets article (and links) describes how to rethink teaching high-frequency words and fit them into phonics lessons.

Dolch Word Lists
The Dolch Word list is a list of the 200 most frequently appearing sight words. This page offers printable lists of the Dolch words featuring artwork from children's book illustrator Jan Brett.

Sightwords
This site offers free printable flashcards for both the Dolch and Fry sight word lists divided by grade level as well as sight word games, and techniques to help teach sight words.

Tips for Teaching Sight Words
This Scholastics article offers a variety of methods to teach sight words for grades K-2.