There was one briefly which selected automatically when you used a mobile browser but this resulted in heaps of complaints from people who who preferred the full one.
I am reluctant to add a "skin" that can be selected by the user. Two reasons behind this:
1) the "lite" skins don't normally let you do all the user profile stuff, including selecting a new skin...so once selected, it is set for that user and even when they get back on their pc its not possible to switch back to the full skin - I found that the hard way !
2) Close to my heart, we can't display adverts on a lite skin. RTG is losing money at the moment anyway, and that would be a further burden as I'd get no revenue from anyone browsing that way. There are ways around this such as charging a small fee to allow use of the skin, but setting it up is all extra work for me and there aren't enough hours in the day.