Online Reference

Hieroglyphs.net
A site by Paul Sciortino, Hieroglyphs.net provides a well designed and thorough dictionary capable of searching for words by Gardiner code or transliteration and also handles English-to-hieroglyph translation. The site also provides a clever sentence composer. A wonderful resource.
A Short Introduction to Hieroglyphs
Although incomplete in parts, this site by Serge Rosmorduc provides a concise and informative introduction to the hieroglyphic writng system.
Wikipedia: Transliteration of Ancient Egyptian
This site provides information on the transliteration of anciet Egyptian hieroglyphs, including information on the various transliteration schemes used by Egyptologists.

Recommended Reading

Collier, Mark, and Manley, Bill. [1998] 2003. How to Read Egyptian Hieroglyphs: A Step-by-Step Guide to Teach Yourself, Revised Edition. University of California Press; Revised edition.
Gardiner, Sir Alan. [1927] 1999. Egyptian Grammar: Being an Introduction to the Study of Hieroglyphs. Oxford: Griffith Institute; 3rd Rev edition.
McDermott, Bridget, and Fletcher, Joann. 2001. Decoding Egyptian Hieroglyphs: How to Read the Secret Language of the Pharaohs. Chronicle Books.