Mo is also used in American politics as a synonym for "momentum." If someone starts their campaign early and gets people involved on a large scale quickly, they are said to have Mo, which is a Good Thing come Election Day.

But the mo I'd rather talk about is a postposition found in Japanese. It is roughly synonymous to the English words "also" or "too." For example:

鈴木さんは日本人だ。田中さんも日本人だ。
Suzuki-san wa nihonjin da. Tanaka-san mo nihonjin da.
Suzuki is Japanese. Tanaka is also Japanese.
Mo can also be used in conjunction with other particles besides wa and ga. Some examples:

イギリスにも行かない。
Igirisu ni mo ikanai.
I won't go to England, either.

演歌も歌える。
Enka mo utaeru.
(He/she/I) can sing enka, too. (In this case, the mo replaces wo.)

In other cases, the "mo" indicates "every" or "any."

どこでもドア!
Doko de mo doa!
Anywhere door! (one of Doraemon's handy tools)

いつまでも愛している。
Itsu made mo ai shite iru.
I'll love you forever (lit. "to any when").

"NTT DoCoMo" = "NTT Anywhere"

Finally, for the sake of completeness, is what cows say in Japanese onamotopoeia, as opposed to mooing in English.

Mo-o-o-o-o-o-o.