Mac OS X Lions get native Ext file system access
Paragon has updated its Linux file system driver for Mac OS X to support Lion and Mountain Lion. ExtFS for Mac OS X 9.0 provides complete read and write access for Ext2, Ext3 and Ext4 filesystems. Paragon's drivers make it possible to create files larger than 4 GB and supports automatic mounting. As a low level filesystem driver, Ext2/3/4 drives appear directly in the Finder and appear as native OS X drives. According to Paragon, there's minimal performance loss compared to HFS+.The company builds its Ext file system driver on its in-house universal filesystem driver which it also uses to deliver NTFS for Mac 10.0. The Paragon ExtFS costs $39.95 and a 10 day trial version is available.
MacFuse was the traditional alternative to software like Paragon's, but it ran in userspace rather than as a kernel extension and so had a penalty on performance. More importantly, the project is no longer actively developed. Since then, projects such as FUSE for OS X which use the MacFuse source have been started; these can use MacFuse support like fuse-ext2 but tend to only be reliable and safe reading the filesystems, not writing them.