For the past two years (give or take), there has been talk about Google’s impending entry into the online payments market. We’ve heard names like Google Purchases, Google Wallet, and Google Payments tossed around, as everyone waits for Google’s “PayPal Killer” (their words, not ours) to be unleashed.

Memorial Day Weekend 2006, the latest Google payments rumor has arrived. Garett Rogers at ZDNet has done some digging and discovered that googlecheckout.com and googlemastercard.com have been registered by Google.

Back in September, Rogers was the guy who uncovered that Google had registered the domain name Gdrive.com through another company, and it took quite a bit of sleuthing to figure the whole scheme out (a.k.a.: MarkMonitor and DNStination, Inc).

The chatter on the Web seems to be focusing heavily on the googlecheckout.com registration — but we’re curious to see what’s in the works with Google and MasterCard. It could be something very similar to the PayPal + MasterCard tie-up; but Google’s also got a history of seeking unique partnerships with large companies.

Could the Googlers be working on something bigger with MasterCard, something that could allow them to make serious penetration into the payments market — both online and off? Plenty will scoff at the size/scale of such endeavors — but Google’s got no shortage of cash to burn pushing into new markets, in a big, big way.

At the same time, MasterCard’s got a HUGE upcoming IPO that would certainly seem to benefit from any high-profile union with stock market darling GOOG. And from Google’s perspective, the only way to milk their current analyst/investor darling status more than they already are is with another IPO; by forging a major partnership with MasterCard (and getting preferred investor status on the IPO), Google could rake in millions.

Keep your eye on this story as it develops.