I use the following little script:

#!/usr/bin/perl -w
use HTML::Entities;
@chr=qw(NUL SOH STX ETX EOT ENQ ACK BEL BS HT NL VT NP CR SO SI DLE 
DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US SP);

printf("DEC\tHEX\tOCT\tBIN     \tCHR\tHTML\n");
printf("---\t---\t---\t--------\t---\t----\n");
for (0..255) {
    printf("%.3u\t%.2x\t%.3o\t%.8b\t%s\t%s\n", 
    $_,$_,$_,$_,$_<33?$chr[$_]:chr($_),$_<33?"":encode_entities(chr($_
+)));
}
[download]

Prints ascii characters or mnemonics, dec,hex,oct and bin values plus the html encoded value.

/brother t0mas