I have an Asus P4P 800-E Deluxe and it runs great in windows 98. It is an 865PE chipset. It has SATA, gigabit ethernet, and USB 2.0 integrated - All working in windows 98. It also has AGP, a floppy controller, Ultra IDE, and other ports that you might want on a retro machine. It also supports 800fsb Pentium 4s, which is nice because these CPUs have a lower multiplier, which allows me to underclock my 3.0ghz model to 1600mhz if I want to by setting an 100fsb. Most socket 478 machines are compatible with throttle and can at least L1 cache disabled, so you can drop them down to a pentium speeds or lower pretty easily. Also, my particular board is pretty cheap and readily available on the ebays. I paid 37$ for it with a CPU and some memory.
Honestly though, any intel chipset on socket 478 is going to work great. Later chipsets have better I/0, so I recommend looking at i865. If you don't need speed sensitivity or ISA slots (although you can do pretty well with certain PCI sound cards), then a socket 478 machine is in my opinion the best platform for windows 98. It is even more stable and fuss free than my slot 1 machines.