I want to put flat bars on my Surley Cross-check and have questions about the brake/shifter dilemma. I've currently got Shimano 105 STI brifters with 105 derailluers. I've got a triple crank and a 9-speed cassette. Will indexed MTB shifters work with that set-up? or do I have to buy the shimano flat-bar series shifters?

The mtb front shifter pulls a different amount of cable so you may have issues up front while the rear should be fine due to identical cog spacing and pull rates on the shifter.

I have such a hatred for indexed front derailers I would fit a decent friction shifter there instead.

Like 65er said, the front derailer will have different pull. You're gonna need either a shifter designed for road pull, or a derailer designed for mtb pull.

A friction shifter would negate the problem, but I think they'd be hard to find anything recent designed for flat bars.

Bar ends with Pauls Thumbies.

I just replaced my Rapid Fire shifters with friction thumb shifters and love them. I snagged mine off an old Huffy (The shifters are actually decent quality too, unlike the rest of the bike) Or you can get some new ones here:
https://www.rivbike.com/products/show...hifters/17-097

My LBS said the pull was the same and you could use Shimano Deore shifters. If that doesn't work, you can definately use Shimano R440 shifters and front derailluer and keep the back 105.

You can try the stock shifters and might get lucky in that they work okay... sometimes you can break the (general) rules and still have things work.

Thanks for all the good advice. I think I'll try the friction shifters, I like the simplicity and the price! Any advice about brake levers? Are there particular levers for cantilever brakes?

Just about any flat bar levers should be ok. Just decide if you want full finger or two finger brake levers.

Awesome. Just went to the guys at LBS and they're putting on low-rise bar, deore rear shifter, friction front shifter and new brake levers in exchange for my old STI shifters. I'm going to put on some serfas bar ends for some more hand positions and it'll be perfect. I can't wait! Thanks for all the input.