so I'm a n00b when it comes to building a bike. I've been looking for something locally that I can "play" with other than my new 7.3FX.
I found a Trek 800. Any opinions on this frameset as a plaything to make into whatever... most likely a commuter / secondary bike?

It's a plain vanilla steel mild MTB with vertical drops. Sure you can have fun with it. It's not a great foundation for you to get all mad scientisty on like a Karate Monkey, etc. Really depends on how far and wide you want to "play" - SS/Fix, 29er, discs it really is suboptimal, but that may not be in your playground. I think it at least has brazeons for a rack and fenders and you could make an adequate MTB-based commuter w/ v-brakes.

here's an 850. It is chromoly, made in Taiwan and works pretty well as a commuter/winter bike/utility

8 series makes a great beater bike. Durable, and a ton of them out there so it's cheap. Don't be getting all upgrade-itis on it since it's certainly lipstick on a pig there and you'll be fine.

-R

Here is my now departed Trek 830. Bought new in 1988, it served me well as a commuter and short tour bike. Finally snapped a dropout. I'm convinced it was a bike trainer that fatigued it - not normal use. As stated before, there is nothing wrong with the 8 series. They are tough, cro-moly bikes, and will run with the big dogs.

I got a well beaten 820 for $20 on CL.
Someone had tried to "fix" the shifters, so I scabbed on a cheap pair of friction shifters from a Wal Mart bike and I had a serviceable back up/parts donor.
Someone then stole the rear wheel from my 86 Rockhopper, so the TREK gave up its wheelset (Free Hub) and now has wheels off a RoadMaster. It's still a serviceable back up!
I was also able to try a different length crank for just my time swapping them. Finding out how much better a slightly shorter crank worked for me was well worth the $20!

Also, it's a good "practice bike" for attempting a repair that is new to me, as a confidence builder. Even if I screw it up, I've still got some "spare parts".

Don't get crazy with upgrade$ and it'll serve you fine as a 2nd bike. Only do an upgrade if you find a part too cheap to ignore!

The 8 series varied through out the years. I put drops on a newer one( don't know the year but it was heavy) it had only a cro- mo main tube. It was oversized hi-ten tubing, China junk compaired to the 88 Tange 5 frame. You may want to reasearch what year, unless its just too cheap of price.

Trek 800 was my first bike and has always had a place in my heart. Its s super durable frame, reasonable weight, very comfortable, long wheelbase, all sorts of braze ons.

I built mine into a tourer and its actually for sale on eBay right now