/var/log/kern.log or wherever your distro leaves kernel log messages is your best bet. Most drivers when they're loaded leave a friendly message in the kernel log detailing that they were loaded and what kind of hardware they found themselves attached to, like:
[ 2.319928] Intel(R) PRO/1000 Network Driver - version 7.3.20-k2-NAPI
[ 2.320078] Copyright (c) 1999-2006 Intel Corporation.
[ 3.954481] PCI: Setting latency timer of device 0000:02:01.0 to 64
[ 4.283544] e1000: 0000:02:01.0: e1000_probe: (PCI:66MHz:32-bit) 00:50:56:99:00:1a
[ 4.324951] e1000: eth0: e1000_probe: Intel(R) PRO/1000 Network Connection