It has secp256k1 in git master, although not in the last release I tried. If you don't want to track head, it's simple enough to monkey-patch in support:
# Import as a different name so as to clearly distinguish from our ecdsa* modules
import ecdsa as pyecdsa
# Certicom secp256-k1, the ECDSA curve used by Bitcoin. This curve has recently
# been added to the python-ecdsa repository, but is still missing from the latest
# version on PyPI.
try:
SECP256k1 = pyecdsa.curves.find_curve((1, 3, 132, 0, 10))
except pyecdsa.curves.UnknownCurveError:
_a = 0x0000000000000000000000000000000000000000000000000000000000000000L
_b = 0x0000000000000000000000000000000000000000000000000000000000000007L
_p = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2FL
_Gx = 0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798L
_Gy = 0x483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8L
_r = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141L
curve_secp256k1 = pyecdsa.ellipticcurve.CurveFp(_p, _a, _b)
generator_secp256k1 = pyecdsa.ellipticcurve.Point(curve_secp256k1, _Gx, _Gy, _r)
SECP256k1 = pyecdsa.curves.Curve('SECP256k1',
curve_secp256k1,
generator_secp256k1,
(1, 3, 132, 0, 10))
pyecdsa.curves.curves.append(SECP256k1)