Hi,

which Wi-Fi mini PCI-E cards are compatible with RBM33G router board? I tried to install Intel Wi-Fi card, but the router have not recognized it at all (no devices in Wireless section).

Only Qualcomm / Atheros cards are supported (like AR93xx,AR94xx,AR95xx, QCA95xx, QCA98xx, QCA6300) but only original Mikrotik cards are officially supported.
If you find non-Mikrotik card with exactly same radio chipset as used in MIkrotik one, it will likely work....