Sure, epic spells are broken as hell, but then again, so is pre-epic spells. I read somewhere that it is possible to summon a solar riding the terrasque as a level 1 wizard, and we all know what kobolds can achieve by level 5.
My point is, that you can break D&D in half long before you can cast epic spells if only you intend to, so in my mind epic spells are no worse than regular spells.
There is a lot of golden epic spells scattered around this forum, but no guide. Do a search, it will come up with some good results.