Visitors to Egypt from the UK require a visa, which can be obtained on arrival at the airport for around £12 (Euros, Dollars or Egyptian currency only) If you're not from the UK, use the great tool at the following link to check if you need a visa. it works for all nationalities. www.visaornot.com

If you intend to stay in Sharm El Sheikh then you do not need a visa.  If, however, you intend to visit the Ras Mohammed national park by road or boat it is advisable to obtain one on arrival.  Although you apparently do not need one if you travel there by boat, other travelers have noted that this is subject to the whims of the officials at the departure point.  For the cost, it is a lot easier to have the visa in your passport than try to negotiate with the police if they say that you cannot embark without the visa. 

If you are only going to your resort in Taba , and not on any excursions, you do not need a visa. At the borders you dont get of the coach, (if travelling with a travel company) they get on and check your passport. 

You DO need a visa to go to Ras Mohammed by boat, and they cannot be purchased after arrival; so if you want to go there DO get visa on arrival - particularly important for all you divers out there, as Ras Mohammed is FAB diving.