You can enhance your skills and attributes through magic. Spells, potions and items can increase your attributes and items can increase your skills. So even if youve reached your max level or just need a little extra "oomph", you can still increase the remaining attributes and skills through the judicious use of magic.
A word of caution, though. If you equip an attribute enhancing item and keep it equipped too long, the attribute will not return to normal when you unequip the item. Instead, it will drop anywhere up to half of its normal value. In order to repair this damage you will need to get healed at a temple or heal the damaged attribute yourself. In order to do it yourself you will need a spell to repair the attribute. In other words, youll need 8 spells if you want to be able to heal each attribute. Its good practice for Restoration, though.
Magic items can also enhance your skills. Typically, an item adds 15 points to the skill. When it breaks or you unequip it, the skill returns to normal. Multiple enchantments of a single skill will not work in a single item. If you want to enhance a skill more than 15 points, you will need to enchant multiple items. Since higher skill levels mean more difficulty in developing that skill, its best not to keep the item equipped while you are resting since this is when the game checks to see if your skills increase. With skill enhancing magic items it is possible to exceed 100% of a skill level. For magic skills, reaching 105% in the skill reduces the casting cost of all spells in that school to 5 points. This does not apply to spells that draw from more than one school of magic.
Interestingly enough, the guilds dont seem to care where you got your skill. As long as the skill meets their minimum expectations, theyll award you new rank based on your enhanced skill. So, you want to be an Archmage, but your highest magic skill is only 80? Equip an item which enhances the skill and theyll award you the new rank (assuming you have the required rep to qualify). And they wont take it away if you unequip the item. On the flip side of this is that the trainers guage your ability based on the enhanced skill, too. So if you want to train, unequip any skill-enhancing items or the trainer may very well tell you that he can't help you. As an aside, the game had originally provided for the possibility of your being demoted by your guild(s). This feature was not implemented in the released version of the game because it caused too many problems. Beware, though, it may resurface in TES3.
Diseases such as Vampirism and Lycanthropy also enhance certain skills and these skills can go above 100%. The game determines your level based on the UNENHANCED skill level. So a Warrior going looking for a Werewolf in order to gain a few levels by contracting Lycanthropy will only get you a hairy Warrior. You will not get a hairy high-level Warrior. More about that in another section.
BUG ALERT: In one recent game I managed to contract Lycanthropy. The next time that I rested, I gained two levels. The game is supposed to determine your level based on your unenhanced skills, but (at least on my system) there appears to be an intermittent bug that counts your Lycanthrope skill level as your real skill level. If this happens to you, you have two choices: reload a game before you contracted the disease or live with it.