I found a quick way of doing “View Source” in Konqueror. The built-in way opens your text editor, which isn't instant in my case (I have it configured to use Kate, which is great if I'm actually going to edit something, but usually I just want a quick peek, and I want it to be instant).
The trick is to use the following bookmarklet:
You can use bookmarklets in Konqueror via 'Minitools' — it's quick and convenient, but so badly documented that I only just found out about it. The page's source is opened in a new window.