LastPass has experimental support for smart card readers as a Premium feature.  Currently, only computers running Windows, Mac OS X, or Linux, SafeSign middleware, and Internet Explorer, Firefox, or Chrome support this feature.  Safari and Opera can be supported by installing an additional binary component.

OpenSC is also supported as an alternative to SafeSign (currently only on Windows and Linux).  Please note that since some browsers still run in 32-bit mode even on 64-bit versions of Windows, you may need to install both the 64-bit and 32-bit versions of OpenSC.