If you mean showing TV network programs on your computer at the same time they are broadcast on TV, you would be looking for ‘shady’ websites.
Day after and later viewing of many programs can be found on the individual TV network websites, on Hulu and Hulu Plus (fee).
If dates (whether current or not) is not an issue, several services offer older series for a fee: Netflix and Amazon.com are the two most used.
You can also purchase individual programs on Amazon.com ($2 or $3 in HD, IIRC) and via iTunes.
Yes, I meant showing TV network programs on my computer at the same time they are broadcast on TV... oh well, thanks.