With the advent of Unicode, legacy character encodings have mostly lost their raison d’être, but they are still in widespread use and are clearly not going to disappear any time soon.
This site now provides PDF charts for ISO-8859 and 8-bit Windows encodings, as well as tests and information on browser support and links to more official and authoritative sources.
There is a WHATWG Wiki page devoted to encoding support in browsers with a focus on labels (MIME charsets), whereas this page is more about the encoding vectors used to map from bytes (octets) to Unicode characters.
One of the most common pre-Unicode encodings, at least in Occidental Europe and parts of the English-speaking world, is Windows 1252, Microsoft’s alternative Latin-1 encoding with a few additional characters compared to the standardised version ISO 8859-1, upon which Unicode is based.
The table to the left shows the missing characters in a chart similar to the ones provided by the Unicode consortium. Indeed, you may want to download this as a PDF and put it in the margin of page 577 of the Unicode 5.0 book for easy reference.
This table was generated using a custom PostScript program which we have made freely available. Please find all the gruesome details about the chart-generating code, complete with examples, on a separate page.