Using ReloadEvery:
Requirements:

• Firefox 1.5-3.x

ReloadEvery is a fairly simple addon.
To use it, simply right click on a page:

Hover over the "Reload Every" entry and you will be presented with a list.
The "Enable" option enables ReloadEvery and sets the refresh time to whatever the selected time is.
The "Enable All Tabs" makes it refresh the page on all tabs at the same time.
The "Disable All Tabs" makes it stop reloading the tabs.

Custom:
The "Custom" button presents a dialog box

Fill in the boxes, click OK, and the page will be reloaded as often as you want it to be.

This is useful for Sports news (OK, or making your entry on UserLogos seem like it has a lot of views!)