To net it out, IBM and Lenovo have announced this recall in cooperation with the U.S. Consumer Product Safety Commission and other regulatory agencies. The recall impacts lithium-ion batteries manufacturing by Sony, and Lenovo will be offering free-of-charge replacement batteries for all recalled batteries.
Model lines affected include the ThinkPad R, T, and X series (Check here for specific model numbers).
If you find that your battery was recalled, in order to safely continue using your ThinkPad, first turn off the system, remove the battery, then power the system back up using only the AC adapter.
To make it easier to identify whether or not your ThinkPad was affected, you can also use this automated solution.
I ran a Technorati query (Technorati is a blog search engine, if you're not familiar with it) a few minutes ago against the query term: "ThinkPad battery recall." You can read more about what folks in the blogosphere are saying about the situation there.
Meanwhile, it goes without saying, but will be repeated here, that both IBM and Lenovo apologize in advance for any inconvenience caused by this recall.