I've been searching endlessly for an Ethernet adapter compatible with my 'new' PowerBook 150 that would allow for Internet connection. I believe that an Asante EN/SC adapter or an Etherwave adapter with an 8-pin mini din connector would be suitable for such a job, but I couldn't find either anywhere. Any help is greatly and immensely welcomed.
Depends on what kind of networking you need. If you need direct TCP/IP over Ethernet, then the Ethernet-SCSI adapters (like the Asante EN/SC series of adapters) will provide you TCP/IP over Ethernet capability. I noticed one actually sold at eBay for a low price over the weekend: #170885870288
The Etherwave adapters only provides an RJ-45 connection, but you don't get real Ethernet -- you get something like EtherTalk (LocalTalk on RJ-45). You could use this with AppleShare/AppleTalk servers, including those that come with earlier versions of OS X. But with these adapters, you don't get TCP/IP unless you have a MacIP server somewhere in your network that provides the translation between AppleTalk and TCP/IP.