If you have a lot of browser windows open that you're not currently using, open this page and type in a title. Now your browser windows will be annotated. Especially useful if you use OSX spaces.

title.html

<style>
input {
    margin-top: auto;
    margin-bottom: auto;
    background-color: transparent;
    font-size: 150px;
    width: 100%;
    height: 100%;
    text-align: center;
    border: none;
}
input:focus {
    outline-width: 0;
}
</style>

<input id="title_input" onKeyPress="onKeyPress()" onKeyUp="onKeyPress()" type="text" />

<script>
var defaultTitle = "(enter a title)";

function onKeyPress() {
    if (window.event.keyCode == 13) {
        var input = document.getElementById("title_input");
        var value = input.value;
        if (!value) {
            document.title = defaultTitle;
        }
        else {
            document.title = value;
        }
        window.location.hash = encodeURIComponent(value)
    }
}

document.title = defaultTitle;
var encodedTitle = window.location.hash.substring(1);
if (encodedTitle) {
    var decodedTitle = decodeURIComponent(encodedTitle)
    document.getElementById("title_input").value = decodedTitle
}
document.getElementById("title_input").focus();
</script>