Apple has seeded Mac OS X 10.7.3 beta build 11D42 to developers. The build comes in at 989.75 MB for those updating from 10.7.2 and 1.26 GB for those updating from any previous version of Mac OS X Lion.
According to MacRumors, Apple has asked developers to focus their attention on Spotlight, Safari, Address Book, iCal and Mail. The release notes contained in build 11D42 indicate that the build will add Catalan, Croatian, Greek, Hebrew, Romanian, Slovak, Thai, and Ukrainian language support, address issues when using smart cards to log into OS X, resolve issues authenticating with directory services and address compatibility issues with Windows file sharing.
Apple's last update to Lion was in October of last year with 10.7.2, which brought support for iCloud to Macs running Lion.