Is it possible to connect a TV to a PC through an ethernet connection?
 I have a VAIO PC that is connected to a cable outlet and can display
and record TV.  And I have a wireless network (G) with a wireless
bridge/5 port switch near a TV.  Essentially, I want to connect the TV
(standard 27" with component and composite connections) to an open
ethernet port on the switch (which is then send wirelessly and
connected to the wireless network and VAIO PC).  I'd like to display
the audio and video of the PC on the TV (and maybe even zoom on
certain areas).  Anybody have any ideas?

Technically it would be possible, realistically the bandwidth through
an ethernet connection would not be enough (unless its gigabit
ethernet) to support a full resolution video and audio out without
compression.

I suspect that this is the reason there are no such devices on the
marketplace.  Of course there are audio/video out cards available for
your laptop that will even fit in the pcmcia slot which will do the
job.  The price range for these is around $100 but you might find an
older model on ebay for even cheaper.

Hope this helps

Can you give me links to such products?  And, yes, it is a Gigabit
network (802.11g).

My fault... I guess it's not a gigabit network... 54 megabits.

Your best bet might be a different tactic. ... video out from source
to a video distribution panel
http://www.automationfaq.com/fom-serve/cache/310.html
or a video modulator http://www.smarthome.com/av_mod.html

Simply stated: create an off-air channel on your local cable line in your house.