The standard bitcoin client jes uses OpenSSL, and all trust about entropy lies on OpenSSL.

But you have other options. If you can access an entropy source and obtain a set of 256 random bits, then you can create your own prov/pub keys (see bitaddress,com) and import them on your wallet (search for pywallet.py)

There are entropy sources over the net, such as random.org and hotbits.com; you can download a lot of random bits from both, hash them and put the hex string in bitaddress.com