Not clones... just other Trappist ales. Chimay is decent, but about as popular as Budweiser around here, so I usually gravitate toward others. My favorite Tripel styles are:
Delirium Tremens - Not a true trappist ale, but actually considered by many to be better than most true Trappist ales. I've had trouble getting this in the bottle with lots of solids ("floaters"). Some distributors will try to tell you this is normal, "there's no problem," but it's not. The floaters are protiens solidifying, due to air getting into the bottle, and they do change the taste a bit. However, if you can find a fresh case of it, this is probably my single favorite triple. Case price is $115 around here.
Maredsous Tripel - excellent brew at only $89 a case. I almost always have this one in the fridge.
St. Bernardous Watou Tripel - I list this one because most of my beer nut group of friends name this as one of their favorites. I think it's good, but it's not at the top of my list. I do often have it, though, since it's part of the St. Bernardous variety pack. THIS VARIETY PACK IS THE BEST SAMPLER OF TRAPPIST STYLE BEERS YOU WILL FIND ANYWHERE. PERIOD. BUY IT. Case price on variety pack is $108 here, Watou Tripel case is maybe $115.
Westmalle Tripel - This used to be my go-to beer. It's good, but I drank it so frequently I got tired of it. It's been a year or two since I've even had it, so it's tough to say much exciting about it.
Victory Golden Monkey - Victory is a local microbrew, but they make some world-class beer. Mostly really hoppy stuff I don't enjoy, but their Golden Monkey is pretty good. It's listed at only 9.5%, but most swear it must be higher (or maybe it contains crack). People seem to do stupid stuff on this brew... people who are used to drinking big ABV beers. Again, not at the top of my list, but it's definitely on my list. Case price is only $60 here, but we're local / might be more in your neck of the woods.
Victory White Monkey - This is just Golden Monkey aged in white wine barrels. It's one of my favorite limited beers to buy, when you can find it. They only make small batches very occasionally. It's not one I'd recommend to someone new to Trappist ales, as it's really a bastardization, but it's a nice change for someone who drinks them regularly. I'm not sure if this is even available in case form, as I've only ever seen it in single 25 oz. bottles.
Allagash Tripel - Made in Maine, of all places. I can't remember for sure, but I think there's some cross-pollenation between Ommegang, Duvel, and Allagash. In any case, it's a good American take on the traditional Belgian Tripel. Never bought this by the case, only the glass. It's not my favorite, but it's a favorite among some of my other beer snob friends.
Allagash Curieux - This is just their Tripel aged in Knob Creek bourbon barrels. It's a super-tasty extra-special treat, for the guy who's had it all. It runs $99.99 per 6-pack around here, but those are 25-oz bottles, so equivalent case price is $200.