The corporate credit markets served up a full plate last week, with Bloomberg reporting more than $38 billion in sales, the most in five months. Just three companies swiped their corporate credit cards for over one-third of the total. Who's doing all that borrowing and what are they doing with the money? Here are a few of the stories.

Amgen (Nasdaq: AMGN) led the borrowing charge with $6 billion in four issues ranging from three to 30 years with coupon rates from 1.875% to 5.15%. It will be using the money to place $5 billion worth of votes in the stock-versus-bond debate by purchasing its own shares. Amgen is the second company to announce a multibillion-dollar share buyback financed with bonds. Intel (Nasdaq: INTC) led the big equity-for-debt charge with a $5 billion buyback announcement in September. And Amgen isn't done. The SEC filing included this, "We expect to engage in financing activity, including this offering, to fund repurchases. Future funding may include issuance of additional senior notes (denominated in U.S. or foreign currencies), term debt and/or commercial paper."

Teva (Nasdaq: TEVA) rolled out $5 billion of new paper in issues ranging from 1.5 to 10 years with floating rates on the short stuff and coupons of up to 3.65% on the 10-year paper. It will be using the money to repay short-term debt used for its Cephalon acquisition. Teva shareholders should be pleased that today's low interest rates make that purchase a little less expensive.

Next in the multibillion-dollar club is miner Peabody Energy (NYSE: BTU) with $3.1 billion of high-yield bonds to finance its acquisition of Australian miner Macarthur Coal. Peabody split the borrowing between a seven- and 10-year private issue with coupon rates of 6% and 6.25%. Peabody is hitching its coal hoppers to the Pacific markets with this acquisition and by moving its chief operating officer to Australia.

Windstream (Nasdaq: WIN) hit the markets with $500 million of 10.5-year paper sporting a 7.5% coupon. It will be buying about $200 million of higher-yielding debt that matures in 2016. The rest of the money will be used to pay down its revolving credit, which will free up that credit line to repurchase some 9.5% debt that comes along with Windstream's acquisition of PAETEC.

Continuing the refinance story, Dr Pepper Snapple (NYSE: DPS) popped the top on $500 million split between seven- and 10-year bonds with coupon rates of 3.25% and 4.5% to refinance a maturing 1.7% coupon note. An interesting take here is that the company chose seven- to 10-year paper to refinance maturing two-year paper. The rate for new two-year paper would have been quite a bit lower, but it chose to lock in rates for the longer term.

All five of these issues show companies continuing to take advantage of low interest rates to buy back shares, fund acquisitions, call higher rate paper, or lock in low rates while they're here. Companies are busy selling bonds to buy equity in themselves or acquire other firms. Foolish investors should think carefully before taking the other side of that trade.