After-hours trading Monday featured plenty of widely held tech issues and a handful of strangers to the volume leader board in what amounted to a fairly slow session overall with little news to drive the action. About 45 minutes into the extra session on Instinet, around 2.3 million shares had changed hands among the top-20 volume movers. Schering-Plough ( SGP), the most active stock, was unchanged at $34.10. In regular trading, the drugmaker climbed 5.7%. OSI Systems ( OSIS) was in second place on the volume leader board, where the shares ticked up 0.2% to $22.25. Stellent ( STEL) was flat at $19.24, and Armor Holdings ( AH) was unchanged at $23.33. Zymogenetics ( ZGEN) was also level with the 4 p.m. EST close at $9.35. Intel ( INTC) and Cisco ( CSCO) were each off 0.4%. Ciena ( CIEN), Microsoft ( MSFT) and Sun ( SUNW) were flat. Ericsson ( ERICY) was gaining 1.1% to $4.53, and Oracle ( ORCL) was slipping 0.1% at $16.34. Actrade ( ACRT) was one of the biggest winners, trading up 11.1% to $15.27. During regular trading, the company's shares were pounded, dropping 45% to $13.75. The company issued a statement saying that it didn't know of any reason for the steep decline.