In Joomla there is a special module called Related Items.
What is does is showing content items that are related to the topic your are reading.
It does this based on the words you placed in the field "Keywords" within the Meta Info tab..
But it has one flaw, you get a complete listing of ALL articles related and that might just be a bit to much.
The Related Items Extended version
There is a module released by http://tomh.gdi.cz/ which is called The Related Items XTD.
It consists of one Mambot (Plugin) and a Module, both are easy to install.
Besides that there is also a special documentation download.
It has a lot of parameters, but luckily you can leave the most part alone.
Just fill in the top section to your own preferences and you should be fine.
SEO part of this module:
It gives search engine robots and visitors to your site extra pages to look at.
Titles are link with text included (internal linking)
You get more page views from you visitors….