I use the one in the link below, which was recommended by Duane Collie of 'My Furniture Forum'. He's a store owner who used to post on the furniture board here. He sells quality leather furniture such as Hancock & Moore and Bradington Young.

Here is a link that might be useful: Leather Master kit

I'd be interested to see what others use too. I have a dark brown leather sofa and matching chair--I recently picked up a spray for leather by McGuires at Target--but I didn't make much of a difference.

I did only the chair--it looked better right after using the spray but after it dried it didn't look any different.

When I originally bought my furniture the saleperson said just to use ivory soap and water to clean the leather but I need something more to condition it.

I've used the Leather Master on car upholstery, leather jackets, etc. - the ink remover is great! Still couldn't do much with extreme temps in the car, leather is cracked (car is 14 yrs old, I forget when driver's seat started wearing and flaking in the wrinkles). Right now on my light-colored sofa I'm just using the Guardsmen wipes that came with it. 10 months later still looks good. But I haven't had any spills, oily hair, etc. on it.

I used Lexol leather cleaner and conditioner (yes, same stuff they use on horse tack) dutifully every month for the first year we had our Bradington-Young leather furniture. Then it slipped in priority to every few months, then a couple of times a year, and now I think it's been three or four years since I've done anything to it. Looks fine, but I never had it in direct sunlight nor exposed to temperature extremes for a long time (like in a car). Now I just wipe it off with a damp cloth if it needs it. It's gotten a LOT of heavy use and often abuse over the 8 years we've had it - spills, scrapes, blood, cat "emissions" - and while it doesn't look brand new that would be a rather outrageous expectation IMO. Only thing wrong with it now is that it needs new seat cushions, the old ones are a bit flattened (but still comfortable).

Now the Lexol just gets used on shoes; used to use it on my leather jacket until the poor thing just wore out (it was at least 10yo).

Crumbs, soda, beer, dog hair, snot, ...

Another vote here for Lexol.

I have used products by Guardian and Stainmaster. They both perform equally well.

Lexol for me too. It's by far the most economical and the best cleaner and conditioner. Which reminds me, my sofas need some Lexol.