Someone must have lit a fire under Apple's (AAPL) App Store review staff last week.

Having drifted along for much of September, approving as few as 58 new apps on a single day, the staff green lighted "an avalance of apps" on Friday according to AppShopper.com. A total of 1,394 new applications were approved that day, 302 of them games.

AppShopper doesn't say whether Friday's haul set a new record, although that seems likely. The previous high over the previous two months was 947, set on July 30.

As of Tuesday morning, there were 81,161 active applications available on the U.S. portion of the App Store, according to 148Apps.biz. New apps are coming in at the average rate of 296 a day, according to that site, down from a peak of 356 in June.

According to Apple's Aug. 21 letter to the FCC, new apps and updates pour into the store at the rate of 8,500 per week, where they are reviewed at least twice by a staff of 40 full-time reviewers.

If Apple hasn't staffed up since then, Friday must have been a very busy day indeed.

"We had heard Apple had had quite a back log of approvals," wrote AppShopper's arn, "so hopefully, they have cleared the queue for now."

Below the fold: AppShopper's full chart and what it reveals about the review staff's work habits.

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Late last week, several news outlets reported that 10,000 iPhone applications had been released on the iTunes App Store — an odometer moment that a site called 148Apps celebrated by creating a clickable mosaic of every icon in the store.

Trouble is, nearly 325 of those Apps had been removed from iTunes, putting the total number of active programs as of last Friday at 9,676 — a figure nowhere near as round or as satisfying.

Well, now you can break out the champagne for real. Arnold Kim, who runs AppShopper.com, reports that the App Store finally passed the 10,000 mark sometime overnight Wednesday. By Wednesday evening, he says, the count had reached 10,062. (See here.)

How does he know? He's got a program that plows through iTunes automatically, counting applications and keeping a running tally.

"It's a moving target," he says, "since developers are constantly pulling apps off iTunes for various reasons. So if an app isn't 'seen' for a period of time, then it is considered removed. And if you verify this by trying to hit the app via direct link, you'll get the 'This item not available in the U.S.' error message."

None of this is to detract from what has been achieved by Apple (AAPL), which created a venue for developers that started with 500 apps on July 11 and grew to 20 times that size in just under five months — give or take a few days.

And even though 148Apps's tribute page still counts hundreds of AWOL programs in its current total (10,465 as of Wednesday evening), we recommend a visit, if only to check out the stats and marvel at the lovely mosaic.

148Apps, by the way, gets its name from the maximum number of applications you can install at one time on an iPhone. (9 pages x 16 = 144 + 4 in the static bar at the bottom = 148). You can load more, but they won't show up in the menu.