Laterst CPU's how do i know and check.

latest intel cpu lineup - ivy bridge, core i3/i5/i5 3000 series, lga1155 socket. example: core i5 3570k, core i7 3770k.
latest amd cpu lineup - bulldozer, fx 8000, 6000, 4000 series, am3+ socket. example: fx 8150, fx 6200.
you can check www.intel.com for intel cpus, specs, datasheet etc.
for amd, www.amd.com
also, http://en.wikipedia.org for amd and intel cpu pages.
for benchmarks and reviews, check tom's cpu charts, search for the cpu you want to find review of.