I have had good results from the TP-Link TL-WN321G and Tenda W311U, both USB devices, both use Ralink chipsets and both support AP mode. The Tenda is supported by the run driver in pfSense 2.0 (but not in earlier versions). The TP-Link devices I used had an older version of the Ralink chipset and were recognised by the rum driver in pfSense 1.2.3. It appears newer versions of this device need the run driver.
I have had good results from the TP-Link TL-WN651G PCI card with Atheros chipset. It appears this card has been superseded by the TL-WN350GD.
I have no experience with mini-PCI cards on pfSense though Atheros cards seem well regarded. PC Engines (http://pcengines.ch) sell a range a mini-PCI cards with Atheros chipsets. However, if I recall correctly, they don't sell direct to EU customers. The web site has links to web pages of distributors in a number of other countries.