Everyone is talking about Barcelona - not the city, the server processor version of AMD's K10 architecture. As Fuad from Fudzilla.com is pointing out, only a fraction of us will invest money in that type of CPUs. So let's talk about the desktop version:
Starting from the Barcelona it sounds very logical that there will be two quad-core desktop versions. The Athlon 64 X4 (2MB shared L3-Cache, codename 'Agena') and the Athlon 64 FX (2MB shared L3, codename 'Agena FX'). There will be a dual-core Athlon 64 X2 ('Kuma'), it's unknown how much cache this will have implemented and last but not least there might be a single-core Athlon 64 ('Rana').
Some of the improvements of the K10 architecture are a faster HyperTransport solution (HT 3.0 up to 4GHz) and improved power saving modes (you don't need a driver anymore for it to work). Both will be supported by the new AM2+ platform. It remains to be seen if the new CPUs will be drop in compatible to existing sockets (losing the HT3 speeds and new Cool'n'Quiet features of course).
Btw.: Fuad is talking about 'Budapest' as well which is a 1xxx Opteron supporting a single socket only.

Update:
After writing this post it came to my attention that there are several more websites knowing something about the K10. In a German forum called Effizienzgurus you will find some more news regarding the whole lineup of processors.

More R610 and R630 Details

techPowerUp! has already reported on some of the basic details of the R610 and R630, ATI/AMD's mainstream and value cards, but now there is a bit more information. The most important things to note are that cards will obviously be DirectX 10 compatible, and both support shader model 4.0. Rather than going into detail about the other specs, I'll let you read the information found in the attached image. Unfortunately there are still only bits and pieces of data, but it gives you a rough idea of what's on offer:

Fudzilla is reporting ATI/AMD might have considerable problems with it's fastest R600 variant. The reason behind is unknown, they are now focusing on the 512 MB DDR3 version and this one will be available at the release sometime in May this year.

NVIDIA is set to launch the mainstream 8600GTS (G84-400) and 8600GT (G84-300), as well as the 8500GT (G86-300), on the 17th of April. The GeForce 8600GTS and 8600GT will have 256MB GDDR3 memories onboard each, both sporting a 128-bit memory interface but no HDMI yet. The GeForce 8600GTS is meant to replace the 7950GT and 7900GS, while the latter will replace the 7600GT. The 8500GT aims to replace the 7600GS.

The 8600GTS will be clocked at 700MHz core / 2GHz memory and comes with dual D-DVI, HDTV, HDCP, but requires external power. Price is estimated between US$199-$249. Another mainstream model, the 8600GT, will be clocked at 600MHz core / 1.4GHz memory and has 2 variants; one with HDCP (G84-300) and the other without (G84-305). This model doesn't requires any external power. It will be priced between US$149-$169.

The last model meant for the budget segment is actually a G84 core but downgraded to meet the value segment pricing structure. The 8500GT will be clocked at 450MHz core / 800MHz 256MB DDR2 memory and comes in 2 variants; one with HDCP (G86-300) and the other without HDCP (G86-305). The 8500GT should see a retail price between US$79 to US$99. The 8300GS, which will be released towards the end of April, is expected to replace the current 7300 series.

The NVIDIA 80nm G84 and G86 line-up will meet head on with ATi's DX10 65nm offerings, where the mainstream RV630 is slated to arrive in May and the value RV610 is slated to arrive earlier in April.