Blogger is fine service, but if you want to write some source code inside of post, you are on your own. However there is solution in form of SyntaxHighlighter [2010-12-31: I swithed to it is WordPress' SyntaxHighlighter Evolved].
From now on you can see code like this:
void Main() {
Console.WriteLine("Hello world.");
}
Plain text samples are also allowed.
Some lines may be highlighted.
But not all need to.
<xmlPart param1="value1" paramX="valueX">
<sub>Test</sub>
<sub>Test 2</sub>
...
This looks great if you have JavaScript enabled.
P.S. This post may change from while to while since I will be using it as testing ground. Unfortunately, you can see how exactly code looks only once you publish post.