See:
http://en.wikipedia.org/wiki/Ralph_Lauren_CorporationHigh quality:
RL Purple Label, RLPL (highest pricepoint, forum favorite, luxury items, more conservative than RLBL)
RL Black Label, RLBL (modern slim cuts, forum favorite, high price but below RLPL)
RRL (casual wear and denim, priced high, very well constructed items)
Average quality:
Polo Ralph Lauren (i.e. RL Blue Label), PRL (the "pony" line since the horse is a polo player; this is the most widely found line, and cheaper than RLBL, but not "cheap" by any means --- priced higher than most high street brands i.e. banana, j crew, etc.; from my experience quality runs all over the place for PRL with average to high quality, never had anything too crappy though)
RLX is their athletic apparel line and quality is decent, but most items are overpriced imo
Ralph Lauren Rugby (aimed at the college crowd to compete with Abercrombie basically, cheaper than PRL, quality is decent, for a while their made in Italy suits were a great bargain)
Below average-average quality:
RL Denim & Supply (basically their version of gap with cheaper priced goods, most stuff is average quality, I only own a few T-shirts from this line)
Club Monaco (this is also owned by the RL parent company, not sure if RL produces anything for CM directly)
Below crappy quality:
Lauren for men (green label) (this is not even made by RL and is crap)
Other lines that I don't know much about:
RL also has a golf line and a tennis line, but I have no experience with these goods