ECS already has a motherboard ready for the brand-new Intel P965 chipset. The P965T-A comes with support for Crossfire and the upcoming Conroe CPUs. In addition to that it offers features like Gigabit Ethernet and 6 SATA-II ports. This might be a good budget motherboard for Conroe, which will be released around end of July.
The lower end version of the new 965 Intel chipsets is called G965. ECS' motherboard is the G965T-M basically all that is missing is the second PCI-Express slot, so you can't run multiple video cards in it. Other than that it offers all the same features as the P965T-A.
One of the cheapest motherboard to support Conroe is the 946GZT-M. It does not use the more expensive 965 chipsets and is a bit more limited on the feature side with just 10/100 Ethernet and two DDR2 memory slots for a maximum of 2GB usable memory.
This reference board provided by NVIDIA shows the new nForce 590 SLI MCP for Intel. It will support Conroe of course and many other new features added to the nForce 590. The board won't be sold like this by ECS, they will engineer an own version of this board.
Many existing ECS boards have been made compatible with AM2, which is basically just a socket and memory slot change.
In addition to that an AMD AM2 motherboard based on the ATI RS485 + SB460 has been released with the RS485M-M. It is a quite basic board but will provide a cheap way of getting going with AM2 if you don't require fancy overclocking or support for multiple video cards.
An even more affordable board is the K8M890M-M which uses the VIA K8M890 chipset. If you take a look at the features you will sure realize that it will be extremely cheap to make and to purchase.
Equipped with the SIS761 the 761GXM-M is offering a way to use AM2 for office systems which will not have the demands of enthusiast or gamer systems. The plate says up to 16 GB of memory supported. With just two sockets I have a hard time imagining that, I guess it's just a typo. Does anybody know if 8 GB memory modules are even planned at the moment?