What were penny stock traders plowing into last week? It wasn't the names you may be thinking. No, the tickers that speculators were buying into recently weren't the companies making the most noise, nor were they the beneficiaries of the best pumping efforts. Last week's most purchased penny stocks - on a net basis - were NextWave Wireless Inc., (Nasdaq: WAVE), Office Depot (NYSE:ODP), and PharmaCom BioVet, Inc. (PHMB.PK).

Let's take a closer look at each one.

NextWave Wireless, Inc. (WAVE)

It's a bit tricky to say this one was 'accumulated' last week, as NextWave Wireless shares were pounded (on high volume, no less) on Friday. Earlier in the week though, WAVE was seeing some heavy buying. So on a net basis, it was up...about 13%.

As for what caused the early runup for this penny stock, the rumor was it short-covering. We find that doubtful though - our data doesn't show a significant change in short positions, and it's not like short were being pressured at the time by any kid of real strength. We chalk up the move to "one of those unexplained things". (Don't read too much into odd stuff - sometimes it's just odd.)

As for the late pullback, NextWave was removed from the Russell 3000 Index, and all the index funds with a WAVE position were forced to dump it in order to maintain the 'indexness' of that fund.

Generally speaking, index additions and deletions have no long-term effect on a stock's value; we don't expect Friday's selloff to linger.

Office Depot, Inc. (ODP)

The bulk of Office Depot's gain came on the news of its private equity deal, which raised $350 million by selling 20% of its shares to a private equity firm. The market cap now stands at $1.26 billion.

The news itself really isn't a reason to celebrate (or buy) - more dilution of an already struggling company. However, the penny stock's chart makes things a little more interesting.

The news may have rekindled an uptrend that began back in March. Granted, all stocks started trending higher in March. ODP is different though... it's been much more consistent in the way it moves. No volatility or indecision (up is up, and down is down).

Bigger picture, it looks as if Office Depot's investors are betting on a recovery, and also betting the company will enjoy that re-expansion. Could be worth following.

PharmaCom BioVet, Inc. (PHMB)

This pink sheet stock has been range bound since early June, waffling between $0.0001 and $0.0002 the whole time. What's interesting, however, is that for 15 of those 16 days, the stock closed at the high for the day. That's not an enormous feat, since a mere one-share trade late in the day can push a stock up $0.0001 (the upside and downside of a penny stock).

Still, it's an interesting persistency from the buyers, and an interesting persistency in the trade volume.

That said, I care less about PharmaCom BioVet's range, and care more about a breakout. If you want to impress me, push shares above that resistance line at $0.0002.

As for what's driving all the activity for this penny stock, it all started when PharmaCom BioVet asked the FDA for permission to start testing its histone deacetylase inhibitor for canines (yes, for dogs).

In the bigger picture, it's a non-event. Asking for permission doesn't necessarily mean the company is going to do the tests, nor does it mean they'll actually develop the tests into a marketable product. The hope of it all, however, seems to be enough for investors right now.

My take? Considering my dog is battling cancer right now (and that her future is still very uncertain), nothing would make me happier than to see this canine-cancer company succeed.  However, in reviewing the press releases issued since September, I just don't see anything all that compelling.

Oh, all the headlines sound great.... headlines like "announces initial location", "announces plans", "update on corporate development", "expands on strategic alliances", "comments on  corporate restructuring", "announces joint venture agreement", and most recently, "to file with FDA".

Rather than talk about what they're going to do though, how about they just do it?  I'm reminded of so many other companies that were forever planning, but never getting anything done.

If I'm wrong, or if I'm not seeing something with PharmaCom BioVet, feel free to chime in below. Just don't tell me the same thing I can read in the press releases though.... give me something concrete and specific.

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