For VMs up to version 1.3 use:
qemu-system-i386 -hda IMAGE -net user -net nic,model=pcnet -boot c -display curses
For VMs from version 1.4 use:
qemu-system-i386 -hda IMAGE -net user -net nic,model=ne2k_pci -boot c -display curses
-display curses is optional
36d52abd6397f16fec708cb3527790af423b7593 amnesiac-netbsd-i386-1.0.img.bz2 21d1fe029470f536896442cd5f28c09c8c767b36 amnesiac-netbsd-i386-1.1.img.bz2 a7edb8fc206602b6bcffeca3fd1fafebbf319840 amnesiac-netbsd-i386-1.2.1.img.bz2 9a7c0b6c07af91acdd08cf528697e0d4f811771b amnesiac-netbsd-i386-1.2.img.bz2 bde8396e024d047157ec32e060e963d06b542bc0 amnesiac-netbsd-i386-1.3.3.img.bz2 05adfc3a312c6f464813a7f3f90c96a44c5ce48f amnesiac-netbsd-i386-1.4.3.img.bz2 0643941c40fc06f2efa801e3ee5caf119a7f264b amnesiac-netbsd-i386-1.5.3.img.bz2 c44e167a9e9cd573c8eb53b19db7ddd3931b9fce amnesiac-netbsd-i386-1.5.3.newhw.img.bz2 00169b0dea8d16db4745c8a85b489e7def6b12a5 amnesiac-netbsd-i386-1.6.2.img.bz2 932fe0031470e4ceea1aa33bf8a12733405a5e2a amnesiac-netbsd-i386-2.0.img.bz2 a393c3abc27592bf5fa5445251d359528f4e3aec amnesiac-netbsd-i386-2.1.img.bz2 42ea7878581a2eb50cb3a785830332f5b00d8789 amnesiac-netbsd-i386-3.1.img.bz2 513f52bd1a59eecd6cae7de71ee7a5f239f80757 amnesiac-netbsd-i386-4.img.bz2 979903530f1deaa93362129a59a76a386866722e amnesiac-netbsd-i386-5.2.img.bz2 d4044bd34b1ba73aaa3d3e254ac399fbaef26d45 amnesiac-netbsd-i386-6.2.img.bz2 bf6bd85132d1f8d08b2b4a2cb1dad6e5fcb0578a amnesiac-netbsd-i386-7.2.img.bz2 1246f3dc8ca6d15e48e6afcddbfa7f694e271ddf amnesiac-netbsd-i386-8.2.img.bz2 22f0dce403ebd19e3fc3effc5483cf33290be9cc amnesiac-netbsd-i386-9.2.img.bz2 a1e945b7459c249e2e261cc8064199e485161191 amnesiac-netbsd-i386-9.3.img.bz2