You have asked one of those religous questons :G
Some people mount a UV filter on every lens and never take it off, feeling it protects the lenses.
Some people refuse to mount a UV filter because it adds another pair of air/glass interfaces to the lens and every lens/glass interface is a soucre of lens flair and image degradation.
I use a UV filter when I feel there is a high risk of troubles like blown sand or salt on a beach or other bad environment, otherwise I shoot without one.
If you do decide to use one make sure it is a good high quality brand, my 105mm filter for my 300mm lens cost just under 300$. Good quality filters are not cheep.
A filter I find much more usefull is a circular poalizer, but it comes with a 2-3 stop cost in light loss. Used right they knock out reflections nicely.
Here it took out all the surface reflections and allowd me to see the boats detailes.
My Flicker Photo stream
The lens hoods are another story, they are very usfull in knocking out stray light that may cause falir and they offer some protection for the front lens element.
I've noticed several manfacturers are no longer including a hood with the lens, and depending on the lens they are not exactly cheep to buy.