I was in the same boat a week ago. I didn't want to buy a new tv for my room (cramped enough already), and I didn't want to buy a new tv tuner card or anything like that for my powerbook (i hear it takes up decent processing power, and I didn't want to take away cycles from the stuff I'm normally doing). So I decided to try to get the cable tv to output to my 2005fpw.
Here's what I did:
1. Went to Goodwill to pick up a $10 used VCR
2. Went to Target and picked up a set of RCA cables for $5 and a coax cable for the same amount
3. Got a universal remote for the VCR
I ran the coaxial cable into the old VCR, and ran the video output port into the composite port on the back of the LCD. Voila! That was all it took to get video working on it. After powering up the VCR and programming the remote, I just selected the composite input and got great results (in my opinion).
Here is an example of what the Bond movie on Spike tonight looks like on it.
A higher resolution picture of another scene is here:
http://proelium.org/pics/random/IMG_1522.JPG
The plus side of doing it this way for me was not having to have the computer on to watch tv, not wasting cycles and creating excess heat for the powerbook, and having a remote so i can watch from bed. And the biggest perk of course is being able to watch the game while keeping track of my computing activities:
It wasn't all this easy though since I still had to worry about audio. Your situation will depend on your equipment, but I had to get an RCA to 3.5mm plug converter to run from the audio out on the VCR to the Rear inputs of my creative inspire 4.1 system (the front inputs come from the powerbook's headphone port. After doing this I now have the computer sounds coming out of the front speakers next to the computer and and the tv audio coming out of the rear speakers on the bookshelf closest to the bed so it works out great. The only downside to this setup is that I have no way of controlling the volume from bed now since the remote only handles the VCR and the audio is going through the computer speakers. It's a minor gripe though.
To the OP, I think a 2005/7 or 2405/7 is a very viable solution for watching TV.