I have examples of my own work on my portolio site which are jpgs/flash, and sometimes do include the url if the site is still the same as it was when I worked on it.

But with companies going from one designer/developer to another sometimes the new site doesn't come up to standard and it doesn't look good if you're linking to what is now a poor site.

So I came up with an ingenious idea of stating on my portfolio page that visitors can view my own work using the green links on each project page, with blue link urls where appropriate for live sites. However I state that I cannot take credit for broken websites, un-validating code or sub-standard graphics. Just keep an eye on any urls on your portfolio and get ready to erase a url if somebody else messes up the site.