Today's Lockup Expirations: Centra Software, Impsat, Quantum Effect Devices, Sequenom, Skillsoft, Telaxis Communications

(TheStreet.com's Ben Holmes, who heads TSC's ipoPros.com subsidiary, keeps a close eye on lockup expirations every week. For more on lockups and why they matter, check out Holmes' primer on the subject. The full current lockup list is published separately. )