I don't much like being limited to using the characters found on my key-board or in the ASCII set.

In some contexts, the resolution is to enter an escape sequence, such as those for HTML or those for Java. In other contexts, the best that I can do is to copy-and-paste the character from somewhere.

With that in mind, I cobbled-together a utility qua webpage for my own purposes, character.php. It's a PHP page because it uses server-side code to generate a table on-the-fly of Unicode characters from U+0020 through U+07FF. (Most of these characters will not be well rendered on most systems, though.) Before that table, it has an assemblage of characters that I frequently want (or that I see as otherwise belonging amongst such characters), such as Greek characters and Latin characters with diacritical marks. And, before that assemblage, it has a couple of JavaScript applets; the first of which converts amongst hexadecimal, characters, and decimal; the second of which converts ordinary strings into strings of HTML escape sequences.

Anyway, I began creäting the page with my own use in mind, but I've extended it a bit to make it more useful to others. I might not implement suggested changes, but I'd certainly consider them.