After the initial burst of excitement on Friday that saw iPad pre-orders coming in at the rate of 25,000 per hour, there was a dramatic fall-off over the weekend.

According to Daniel Tello, the Venezuelan blogger-analyst who has been tracking order numbers submitted by volunteers at Investor Village’s AAPL Sanity board, orders on Saturday and Sunday slowed to an estimated 1,000 per hour.

Tello, who is better known on the Web as Deagol (after a Hobbit in J.R.R. Tolkien’s The Lord of the Rings), attributes roughly half of the estimated 120,000 first-day sales to “pure overexcited fanboism.”

The real demand for Apple’s (AAPL) tablet computer in the weeks before its April 3 release, he says, is probably closer to 30,000 per weekday and half that on weekends.

“With three weeks and two weekends left before they ship, I wouldn’t expect much more than half a million in pre-orders and reservations,” he says.

“My best guess, although very tentative given the early stage and few data we have so far, would be that they hit the 1 million unit milestone by the second week after it ships,” he told Fortune. “But this is a very speculative guesstimate based on just a weekend of pre-orders.”

Tello’s estimates are based on 120 orders for 137 iPads over 58 hours, starting at 8:30 a.m. ET Friday.

Working with Victor Castroll, an analyst with Valcent Financial Group, he applied a complex formula that subtracts the average number of non-iPad orders on Apple’s online site (assuming a slight bump due to increased traffic), multiplies the result by an average of 1.125 iPads per order and adds an estimated 2,000 units for the eight late-night hours for which they had no data.

Tello’s bottom line estimate: 152,000 pre-orders by midnight Sunday. This does not include iPads reserved for pick-up.

The breakdown of orders by flash drive capacity (16, 32 or 64GB) and network (Wi-Fi or Wi-Fi+3G) remains roughly where it was on Friday (see pie charts here), with buyers favoring Wi-Fi over Wi-Fi+3G by more than 2 to 1. There was a slight increase over the weekend in 64GB orders, pushing its share of the pie to more than 35%.

Tello and Castroll hope to continue their analysis, but they are running out of volunteers willing to submit their order numbers. If you pre-order an iPad between now and April 3 and would like to contribute to their effort, send the information to ipadsales10@gmail.com. Include your order number with the last three digits Xed out, the number of iPads you ordered, the order time, time zone, memory capacity and whether your iPad is Wi-Fi only or Wi-Fi + 3G.

Tello is famous in Apple investor circles for making predictions of the company’s quarterly revenues and earnings that are as good as, and more often better, than those published by professional analysts. See, for example, How the analysts got it so wrong. You can follow his work at Deagol’s AAPL Model.

See also:

• Day 1 estimate: 120,000 iPad sales
• Apple sells 50,000 iPads in two hours
• The wild iPad Ruckus begins
• How many iPads will Apple sell?

[Follow Philip Elmer-DeWitt on Twitter @philiped]