Here you can find a listing of motherboards that users like you reported as being able to change fan speeds. This is a subset of the hardware that SpeedFan can properly work with. Please note that this is not the listing of the motherboards where SpeedFan is able to access readings from temperature sensors and S.M.A.R.T. hard disks. As an hardware monitoring tool, SpeedFan can work almost on every hardware. I do add new references here based on several reports from end users. If you are going to report a new motherboard, please tell me (at changes [at] almico.com) about how smooth the control is. If the control looks like an ON/OFF one, please, have a look at the "What is PWM and how is it used to control fan speeds?" article and check the PWMOUT option (if any) in CONFIG / ADVANCED.
Disclaimer: I'm doing my best to keep this list up to date and as reliable as possible. Don't blame me if the revision of the motherboard you've purchased can't change fan speeds the way you hoped :-)

Manufacturers ABIT 101 ACER 2 ACORP 68 ALBATRON 146 AOPEN 43 ASROCK 57 ASUS 204 BIOSTAR 78 CHAINTECH 6 COMPAQ 3 DELL 8 DELTA 1 DFI 17 ECS 21 EPOX 10 EVGA 2 FIC 5 FOXCONN 4 FUJITSU/SIEMENS 3 GIGABYTE 48 HP Compaq 3 IBASE 1 IBM 4 INTEL 17 IWILL 5 JETWAY 1 KOBIAN 2 MATSONIC 1 MERCURY 1 MSI 62 PROCOMP 1 QDI 6 QUANTA 1 SAPPHIRE 1 SHUTTLE 26 SOLTEK 5 SONY 9 SOYO 8 SUPERMICRO 2 TOSHIBA 1 TRANSCEND 1 TRIGEM 2 TYAN 8 XFX 1

Motherboards from INTEL that can change fan speeds Manufacturer Model Chipset CPU Notes INTEL D815EEA Intel 815E FC-PGA INTEL D848PMB Intel 848P Socket 478 INTEL D850EMV2 Intel 850E Socket 478 INTEL D850GB Intel 850 Socket 423 INTEL D915GUX Intel 915G LGA775 INTEL Desktop Board D101GGC ATI Radeon XPRESS 200 LGA775 INTEL Desktop Board D865PERL Intel 865PE Socket 478 INTEL Desktop Board D915GAG Intel 915G LGA775 INTEL Desktop Board D915GEV Intel 915G LGA775 INTEL Desktop Board D945GTP Intel 945G LGA775 INTEL Desktop Board DG31PR Intel G31 Express LGA775 INTEL Desktop Board DX38BT Intel X38 LGA775 INTEL Desktop Board DX58SO Intel X58 Express LGA1366 INTEL Server Board SE7500CW2 Intel E7500 Dual XEON INTEL Server Board SE7505VB2 Intel E7505 Dual XEON INTEL VC820 Intel 820 Slot 1 more... There are 16 MOTHERBOARDs listed here.