This is a monster deal in the online world. Priceline.com became the most valuable online travel agency behind a vigorous marketing effort featuring William Shatner, which he did in exchange for company stock. That deal has netted him profits that some suggest are near $600 million after the company’s shares bottomed out during the dot-com bust — the stock price at today’s close was $627.87. Now Priceline is acquiring Kayak Software Corp for $1.8 billion in cash and stock. Kayak shareholders will receive $40 a share, a 29% premium over its closing price, and the stock surged above $40 in after-hours trading. The deal includes $500 million in cash and $1.3 billion in equity and assumed stock options, Bloomberg reports. Kayak debuted its IPO in July.