Super 8 cartridges and 16mm film reels are still readily available and widely used, in B&W reversal and negative (not S-8), colour reversal and colour negative although for colour neg with super 8 it has to be telecined (transferred to digital) as Kodak discontinued the print stock several years ago (but there is a lab in Germany who have custom cut down stock and do the only printing service in the world).
If you want E-6 for your Lomo you need Kodak EKTACHROME 100D Color Reversal Film 5285/7285, it can be processed in ordinary E-6 chemicals , Kodak's motion website is an excellent resource for this sort of thing.I would sit down though when you read the cost...
http://motion.kodak.com/motion/Products/Production/index.htm
Motion picture film is protected by a 'rem jet' backing, before processing this needs to be dissolved in an acid bath (Kodachrome had this as well) so it makes ordinary labs unable to develop it as well as the film perforations being different on motion film. For this I would either try Tecnicolour UK (who you've probably heard of and do processing for some of the most major films in the world such as Harry Potter!) or Andecfilm (the lab I mentioned above in Germany who do about every known service
http://www.andecfilm.de/html/preisliste_eng.htm) but I would not expect it to be cheap (e.g Andecfilm charges 0.70 EUR per meter for developing and film usually comes on a 400 or 1000 foot roll!)
For something cheaper to try out, why not just pick up a Cannon Super 8 camera on ebay? Their widely regarded as the best Super 8 cameras and can now be got for about £30, reversal film and processing is about £15 total in the UK and then either get it telecined at the lab and/or even better get a super 8 projector as these are readily available cheaply (unlike 35mm projectors who's cost second hand usually runs into the £1000's!) Remember you only get 3 mins out of Super 8 cartridge so make it count and theres no sound - you can get a lot into 3 minutes though.