I originally encountered them when I taught 6th grade Language Arts. They were presented to students in an enrichment activity, but certainly plague people of all ages! Here are some visual ways to remember the correct spellings.

Submit your own homophones!

Homonyms are: One of two or more words that have the same sound and often the same spelling but differ in meaning, such as bank (embankment) and bank (place where money is kept).

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

More problematic word sets:

• air heir 'ere
• hair hare
• read read (past tense) red
• 1 car 2 cars
• 1 fish 2 fish
• 1 mouse 2 mice
• 1 goose 2 geese
• 1 moose 2 moose