Taken from the Unix Programming Environment by Brian Kernighan and Rob Pike (pg. 76):

____________________ Table 3.1: Shell Metacharacters ___________________

>               prog >file direct standard output to file
>>              prog >>file append standard output to file
<               prog <file take a standard input from file
|               p1|p2 connect standard output of p1 to standard intput of p2
<<str           here document: standard input follows, up to next str on a line by itself
*               match any string of zero or more characters in filenames
?               match any single character in filenames
[ccc]           match any single character from ccc in filenames; ranges like 0-9 or a-z are legal
;               command terminator: p1;p2 does p1, then p2
&               like ; but doesn't wait for p1 to finish
`               run command(s) in ...; output replaces `...`
(...)           run command(s) in ... in a sub-shell
{...}           run command(s) in ... in current shell (rarely used)
$1, $2, etc.    $0...$9 replaced by arguments to shell file
$var            value of shell variable var
${var}          value of var; avoids confusion when concatenated with text; (see also Table 5.3)
\               \c take character c literally, \newline discarded
'...'           take ... literally
"..."           take ... literally after $, `...` and \ interpreted
#               if # starts word, rest of line is a comment (not in 7th Ed.)
var=value       assign to variable var
p1 && p2        run p1; if successful, run p2
p1 || p2        run p1; if unsuccessful, run p2