Moon dust can be turned into solar panels so in theory you could have a moon base that is sustainably powered by vast tracts of solar panels. Then you could have lunar mining to provide the raw materials, agriculture and manufacturing in several lunar bases. A Mars colony could be established and survive via solar panels and gain raw resources either from the red planet itself, or from asteroid mining, only one base is required for this and their'll likely be one on the moon. If your wondering, according to atomic rockets (link in the sidebar) for a population to survive 1000's of years without genetic problems, you need 500 hand picked breeding age colonists, so preferably 1000 unrelated breeding age colonists from all corners of the world. For the purposes of this thought experiment, assume this system goes through the process of being created now and then being finished and made self-sufficient by the next major empires (most likely some combination of BRICS) within several decades.
So what could they trade with each over, and to facilitate this trade we can assume a Space elevator is built (This is to allow trade with minimal energy expenditure). An important point about building space elevators is that the first one is incredibly expensive, but after that their incredibly cheap (relatively speaking). Since this is a thought experiment we can go all the way and assume with during the recovery from overshoot an orbital ring is built around the equator with multiple elevators. The orbital ring contains foundries, factories and few of the other things that would make sense in space (despite likely being controlled by the ground, this is part of the space economy). So trade could occur from most parts of the planet, so the question remains what could be traded and what interactions could exist.
I remember an article about manufacturing in space and its advantages, such as steel being of a higher quality and the ability to extract purer substances than otherwise. So on the orbital ring part it would make sense for iron ore and other raw metals to be processed and then be shipped down, much of this would also be used for space based manufacturing, only some of which would return to Earth. Food would likely be sent up as payment. And remember this is all taking place while most of the earth is in a low tech state (relative to the space stuff or even current civilization). Thus one potential trade is that of primary goods (food and raw ore) in exchange for high quality secondary goods (space steel) as well as some tertiary goods (computers, solar panels etc).
The space economy could additionally provide information services, say weather pattern data or such along with satellite communications. Otherwise it would provide high class materials or chemicals (its easier to purify things in space), along with advanced manufactured components that only need a power source. Niche items would be in high demand, such as solar panels for remote areas for example and jet aircraft.
So given that the above scenario is unlikely, its a thought experiment after all, how could we see this dynamic in the future. Well we already do, already mentioned is the proliferation of mobile phones in the third world. The Africans who have started to use them as adhoc banks and call time as a stable currency, are exploiting a high technology in a profoundly innovative way. It also points out the benefits to a low tech economy that has access to a limited, but useful, set of high tech equipment. There's a flash game on the internet called 3rd world farmer, have a look, its a simulation of life as a third world farmer, and the first upgrade under the light bulb tag is communications. Its a picture of a mobile phone and it explains that with a communication network farmers can coordinate sales and get a higher income. A self-contained, easily powered communication set makes perfect sense in the rural third world, which is why mobile phones are popular there. Other things like solar panels to power remote clinics, wind generators on ships to power fridges and other relatively high tech gadgets also make sense.
After the peak there are quite a few goods an ecotechnic society could trade with the various non-technical societies, like agricultural, horticultural or rancher based societies and other ecotechnic societies with access to different technologies. Low energy use computers to be used for bureaucracies or mathematical modelling that can run on simple renewable technologies could easily be in high demand. Certain military equipment, especially if it can be maintained easily, would be highly sought after by governments trying to compete and along with high precision manufacturing equipment for various industries. The criteria is an artifact that when built can then be easily maintained or run with the sort of inputs a low-tech society can provide. This is actually separate from the requirements to create a technology. Think of the latter as set up costs and the former as running costs.
This is one of the likely interactions that ecotechnic societies will have with other civilization types (such as salvage societies) and internally with its differing tech sections (due to the vagaries of geography and local resources). Trading certain high tech goods that the other economies find useful but can't produce on their own, for raw resources and goods so that the ecotechnic economy can specialize more than otherwise would be beneficial to both sides. The driving force is simply the varying local resources, manufacturing capabilities and depending on how it turns out, the resurgence of sailing for international trade.