Ramadan in 2009 will start on Friday, the 21st of August and will continue for 30 days until Saturday, the 19th of September.
Ramadan is a great time to visit a Muslim country. don't forget Egypt isn't just about antiquities but also about the people and the culture. Over 80% of the population are Muslims the rest being Coptic Christians and even the most lax and laid back make a special effort during Ramadan
Effects on tourist visiting sites - none what so ever, drink what you like, eat what you like, smoke what you like. I think it is nice not to smoke in a car when the driver is fasting but actually I think it nice not to smoke in a car full stop. Some drivers are very macho about their fasting and like to show how strong willed they are.
Effects on tourist in hotels - none what so ever, often the Christian staff do day time and Muslims night so don't assume everyone you see is fasting
Availability of alcohol - reduced during Ramadan although this is generally sold by Christians it does stop during Ramadan and strict Muslims will not handle it. 5* hotels are not affected.
Effects on tourists non tourist sites, banks, etc these often keep different hours during Ramadan generally closing for Iftar (the sunset meal) so just remember to go early in the day.
See the above page for the rest of Jane's excellent advice.