The following information was pulled from Cunningham's Encyclopedia of Magical Herbs (2nd edition) on magical uses/meanings of clovers. (highly recommended book for anyone interested in herb magic)
If you find a two-leaved clover, you shall soon also find a lover.
Trefoil, or the three-leaved clover, is worn as a protective amulet.
The four-leaved clover, if worn, helps men avoid military service. It also protects against madness, strengthens psychic powers, enables you to detect the presence of spirits, and leads the wearer to gold, money, or treasures. If two people eat a four-leaved clover together, mutual love will result. Seven grains of wheat laid on a four-leaved clover will enable one to see fairies. If you put a four-leaved clover in your shoe before going out you will increase your chances of meeting a rich new love.
The five-leaved clover is powerful for attracting money, and should be worn for this purpose.
White clover is used to work against hexes, and is worn or scattered around the premises for this.
This clover, added to the bath water, aids you in dealing with financial arrangements of every kind. Red clover is also used in lust potions and the infusion is sprinkled to remove negative spirits."