Hard to answer this question due to the number of possible answers but you can try the following:
Testing: xUnit or nUnit. FsCheck, Fuchu and FSpec, if you want to try a more functional approach. SpecsFor, BDDfy, Fixie, Machine.Specifications for BDD and other approaches.
Mocking: NSubstitute or FakeItEasy
Database: Simple.Data, PetaPoco, Massive for Micro ORM's. Entity Framework and nHibernate for full featured ORM's.
Build: There isn't a Maven/Gradle comparison but you can use NuGet, MSBuild, Fake, pvc build, etc.
Testing: xUnit or nUnit. FsCheck, Fuchu and FSpec, if you want to try a more functional approach. SpecsFor, BDDfy, Fixie, Machine.Specifications for BDD and other approaches.
Mocking: NSubstitute or FakeItEasy
Database: Simple.Data, PetaPoco, Massive for Micro ORM's. Entity Framework and nHibernate for full featured ORM's.
Build: There isn't a Maven/Gradle comparison but you can use NuGet, MSBuild, Fake, pvc build, etc.
Logging: ELMAH, NLog, Glimpse, Serilog
If you need other suggestions, let me know.