Here are some of my fav alt codes. Just hold onto the alt key and the punch in the numbers shown ON THE NUMLOCK PAD. Then, you should get the symbol.

þ~0254 (You can use this one for a smiley face :þ)

™~0143 (This is a TM symbol incase you haven't noticed)

©~0169 (A copyright sign)

®~0174 (This is a popular little symbol)

¤~0164 (A little squarish design thing- no idea what its used for)

¢~155 (Cent sign)

õ~0245 (an 'o' with a wavy line on the top)

ô~147 (an 'o' with an accent sign)

»~5544111 (double arrows pointing right)

«~174 (double arrows pointing left)

¡~8877 (an i)

ç~0999 (a 'c' with a curly tail)

Þ~0222 (a smaller tongue, also used for smileys :Þ)

†~0134 (a cross)

‡~0135 (a cross with an extra line)

ø~0248 (a cool saturn symbol)

È~0200 (an 'e' with a line thingy)

Ö~153 (an 'o' with two dots on top, kinda looks like a face with a wide open mouth, hehe)

ò~149 (an 'o' with a little line thingy)

Î~0206 (an 'i' with an accent)

Ü~154 (a 'u' with two dots on top)

û~150 (a 'u' with an accent)

Ï~0207 (an 'i' with two dots on top)

Ë~0203 or.. 1168 (an 'e' with two dots on top)

ù~151 (a 'u' with a line thingy on top)

Ì~0204 (an 'i' with a line thingy on top)