(Updated from 7:20 p.m. EDT)

Pump up the volume. Pump up the volume. Trade! Trade!

It is Friday night, and it is on precisely these sleepy summer evenings, when volume is thinner than an undernourished runway model, that sly stock jobbers can blow stocks around with little breath.

Yahoo! ( YHOO) had little to shout about today. The Internet stalwart settled a relatively modest 2% higher as TheStreet.com Internet Sector index, the DOT, finished up 1.5%.

There was some news. Apparently one of America's most visited portals was also the top Web site in Singapore for the month of June. Also, Internet telephony got some media buzz today and Yahoo! happens to own a stake in Internet dialing company Net2Phone ( NTOP).

None of these tidbits were likely to move the stock, and most likely, Yahoo!'s gain of 1 to 134.93 was the work of an opportunistic trader.

Read-Rite ( RDRT) pulled in the buyers today, ending the session 16% higher. Magnetism doesn't just describe the company's performance today, but also its business. The California tech company supplies magnetic recording heads for the hard-disk-drive market.

Since it hit its 52-week-low of $1.84, on June 22, the company has been slowly recovering. Wednesday's third-quarter results helped speed the climb. The company announced a loss of $37.7 million, or 66 cents a share, on sales of $140.9 million, an improvement over the $44 million loss in the second quarter and the $50.5 million loss in the year-ago period. Also, shipments grew by 10%. Tonight profit-taking set in after two days of sharp gains, taking the stock 10 cents lower to 4.99.

Trader chat rooms are not always the nicest place to play. There is usually a lot more profanity than profundity and truth isn't always served up as ordered.

Crossroads Systems ( CRDS) was the subject of colorful discussion in one such chat room. The provider of storage routers for fiber-channel storage area networks rose almost 30% today despite being slapped with a class-action lawsuit on Wednesday. Typically these lawsuits don't roil share prices too harshly, but there was little news to explain the buying. Some chatters implied that eager bargain-hunting was responsible after a 52-week low of 4.25 hit on July 28. Another trader alleged stock manipulation. Whatever the reason, Crossroads was the most active issue on Island, trading 1.87, or 22%, higher to 10.12 on 320,000 shares.

On Wednesday traders dumped PhyCor ( PHYC) shares, fearing that the company would be delisted from the Nasdaq after recording damages of $350 million to $450 million in the second and third quarters, due to the write-off of assets.

Thursday, the Tennessee-based operator of medical clinics sold some of its assets to the Grove Hill Medical Center in an effort to restructure its relationships with the clinics it manages. PhyCor received about $15.5 million in proceeds, a price exceeding the net book value of the assets.

Today the company settled up 42%, gained 10% in early postclose trading and then drifted lower to a flat 88 cents.

The shares of Emulex ( EMLX) rallied 42% during the day session after the data network company reported better-than-expected results.

The surprisingly strong performance boosted analysts' confidence in the company's business model. The day's flood of buying shrank to a trickle, as Emulex rose 1.31, or 2%, to 69.25.

CAIS Internet ( CAIS) jumped 24% today on news that Microsoft ( MSFT) poured $40 million into the broadband Internet access provider for businesses and hotels. The companies are developing a co-branded portal for the hospitality industry.

CAIS will report second-quarter results Monday, with consensus expectations calling for a loss of $1.17 a share. Meanwhile, the after-hours party continued to rage as the Internet company gained an additional 37 cents, or 3.8%, to 10.37.

10 most active stocks on Instinet (6:30 p.m. EDT)
Company Price Change Session Volume
U.S. Bancorp (USB) 21.3125 -0.0625 94,200
WorldCom (WCOM) 37.50 -0.125 84,200
Cisco (CSCO) 65.6875 +0.125 83,266
Innovative Solutions (ISSC) 12.1875 0 77,300
Intel (INTC) 62.8125 +0.25 67,719
Avon (AVP) 39.4375 -0.4375 66,500
Oracle (ORCL) 81.50 -0.0625 65,223
Crossroads Systems (CRDS) 10.125 +1.875 62,265
Microsoft (MSFT) 69 -0.125 61,190
3Com (COMS) 18 +0.0626 53,924

This information is provided by Instinet, a wholly owned subsidiary of Reuters (RTRSY). For further information, please contact Instinet at www.instinet.com.

10 most active stocks on Island ECN (7:30 p.m. EDT)
Company Price Change Session Volume
Crossroads Systems (CRDS) 10.125 +1.875 323,650
3Com (COMS) 18.125 +0.1875 25,550
Cisco (CSCO) 65.75 +0.1875 23,715
PhyCor ( PHYC) 0.3125 0 23,285
Read-Rite (RDRT) 4.99 -0.10 18,700
PeopleSoft (PSFT) 24.00 0 18,660
Emulex (EMLX) 69.25 +1.3125 16,692
Qualcomm (QCOM) 64 0 16,063
Citrix Systems (CTXS) 15.29 +0.3525 15,625
Onyx Pharmaceuticals (ONXX) 16.375 +0.125 15,490

Island ECN, owned by Datek Online, offers trading, mainly in Nasdaq-listed stocks, from 7 a.m. to 8 p.m. EDT.

Confused? TheStreet.com explains how the rules change when the sun goes down in Investing Basics: Night Owl, a section devoted to after-hours trading.