I'll start with my first one.
Creating a Tips/Quotes section - when your not using the ad section yet.
I have added a clunky bit of javascript that shows famous quotes/tips in the ads section of my site accountingEcho. This is so the site has a little bit more content, until the site is big enough to adverstise.
Here is the code, add it to the sidebar or sidebar-low section. This code shows the quote and the person (in attr) that made the quote (replace X for the number of quotes/tips items you want to use) :-
<script language="JavaScript">
var rand = Math.floor(Math.random()*X) + 1;
var quote = new Array();
var attr = new Array();
quote[1] = "Quote 1.";
quote[2] = "Quote 2.";
quote[3] = "Tip 3.";
quote[X]...
attr[1] = "Quote By 1";
attr[2] = "Quote By 2";
attr[3] = "";
attr[X]...
</script>
<script language="JavaScript">
document.write("<h3>'");
document.write(quote[rand]);
document.write("'</h3>");
document.write(" - ");
document.write(attr[rand]);
</script>