Lennar Projected 2013 sales growth: 34% Investors will look back at 2012 as the year that housing got up off the sickbed. Both home prices and the sales of existing homes have been rising at a nearly 10% pace for much of the year, and in an industry where psychology matters, success is likely to beget further success in 2013 as the huge swath of American renters finally decide to become homeowners. Lennar ( LEN), a homebuilder of mid-priced homes (the average of the 11,000 homes it built in 2011 sold for $244,000), spent the entire downturn cleaning up its act, shedding bloated land holdings, cutting overhead and shoring up its balance sheet. Nowadays, Lennar is one of the leanest operators in the business, with gross margins in the low 20's, several percentage points above the industry average. You can see the industry's projected upturn by gauging this company's top line. Sales are on track to rise more than 30% in 2012 to more than $4 billion, and could reach nearly $5.5 billion in 2013, according to analysts. And the strength should continue into mid-decade as housing rebounds tend to last for several years. Alexion Pharmaceuticals Projected 2013 sales growth: 31% While many drug companies aim to grow through the sale of a range of pharmaceuticals, this company is a one-trick pony. Its lone drug, Soliris,which treats a rare blood disease called paroxysmal nocturnal hemoglobinuria, has been a clear success. Sales of Soliris have risen at least 40% in each of the past five years (to $783 million in 2011), and sales show no signs of slowing down. Analysts expect Alexion's ( ALXN) sales to exceed $1 billion in 2012, and approach $1.5 billion by 2013. Per share profits are likely to eclipse $2 this year, handily beating the record $1.63 in 209, before hitting $2.80 a share in 2013, according to analysts. Amazon.com Projected 2013 sales growth: 28% It's a broadly accepted notion that once a company grows sufficiently large, the rate of growth must invariably slow. Indeed the "laws of bigness" almost always kick in for every firm, though Amazon ( AMZN) CEO Jeff Bezos never got that memo.