Normally I'd tell people to write their own spells where ever possible, as for me, my own spells always seem to work a lot better than spells other people have written. But here are a few basic examples...

Spells and Magic - that said if you do want a site with a large listing of different spells, I would reccomend this site.

Basic Spells
One of my favourites simple spells:-
(Feel free to swap bus for things like train, of course :) ).

"I call upon the goddess and the god
To keep me from missing my bus."

Basic Protection Spell:-

"I call upon all that is good & right
To protect me from that would do me harm
Now and for all time."

Good Luck Spell:-

"I call upon the gods and the goddesses
To bring me the good luck I need to ???
I am grateful for all your help."