There are three really great categories of active mid layers-
Basic fleeces, grid fleeces, and hybrid/ active insulation.
For basic fleeces depending on your operating temperature and output great choices include peloton 97, kuiu peloton 200, outdoor research, mountain hardware, columbia, eddie bauer, and a whole host of others make great "normal" fleeces that fit well, hold up to abuse and will do a great job.
For grid fleeces, sitka has their midweight zip t, heavyweight hoodie, first lite has their klammath, stone glacier has their helio hoodie, kryptek has 2 options, cronos and one other, midway usa has an unreal value option in the elk horn, as well as final approach, rogers in house brand, and a ton of others.
For hybrid active insulation, sitka has the ambient series, stone glacier, outdoor research has a good one, outdoor vitals is about to release a really good one and there are a few others.
It comes down to use case, and price range. If you let us know your use case and your price we can help you out.
@mtwarden did a fantastic review of multiple midlayers and is a voice of reason when it comes to real world use. He's a man who vets something out with real hard use and I'd take his word on any product he deems good.