BenQ 1640 seems to be one of the more highly regarded ones at this point in time. Excellent burn quality, under $50 or so.
Here is a recent AnandTech 16x drive roundup:
The BenQ came out on top:
The only drive we saw that could write to the majority of discs and quickly at that was BenQ's DW1640. It had average performance on most of the benchmarks. but always had a successful read to go with the successful write. The only disc that it could not write to was the MKM A03 8x DVD+RW.
Besides that single issue, the DW1640 has features to aid in successful writes, as well as bitsetting features to allow greater compatibility of the media to which it writes. The bitsetting utility can be downloaded from BenQ's website. Over these 6 DVDR units, we recommend the BenQ DW1640 for its performance and reliability in writing to various types of media. Expect this drive to start showing up on retail store shelves very soon.