An Intel Atom is the lowest cpu that Intel makes. They are not very good for anything more that browsing the internet and listening to music. The are mostly found in net books. I think that you should go with the "i" series, if you are looking into a new pc.
That would be "lowest consumer CPU" no? Don't they still make embedded processors like the 8051 family? <googling...> No, not any more! It does look like the Atom holds the place at the low end.
In addition to the netbook, they are useful anywhere low power and not a lot of horsepower are desired. I have one running my NAS. In addition to serving files and, fetching podcasts and managing my backups, It is crunching BOINC/Rosetta work units and may actually crack 200 RAC.