Top 20 NuGet mono Packages

Fixed viewport image cropping library for Android with built-in support for Picasso, Glide or Universal Image Loader.
BadgeView for Xamarin.Android
TheFinestArtist's Annotations
Round Corner RelativeLayout for Xamarin.Android
Apache Commons Net library implements the client side of many basic Internet protocols such as FTP/FTPS, FTP over HTTP (experimental), NNTP, SMTP(S), POP3(S), IMAP(S), Telnet, TFTP, Finger, Whois, rexec/rcmd/rlogin, Time (rdate) and Daytime, Echo, Discard and NTP/SNTP
The Apache Commons CLI library provides an API for parsing command line options passed to programs. It's also able to print help messages detailing the options available for a command line tool.
Write your app using System.Net.Http, but drop this library in and it will go drastically faster. This is for Xamarin.Android only.
Lightweight Image Cropper for Android which also supports no-crop feature
Simple wrapper library for Android ImageView. If you need an always square or rectangular Imageview, SquareImageView is for you.
LocationProvider is a tiny library that abstracts away a lot of the pain of getting a users location from the phone (without having to call location APIs), provides a fully configurable standard Builder pattern and a set of callbacks.
Xamarin.Android Binding for Qstumn's https://github.com/qstumn/RadarChart
An android view that justifies the text. Gives support to older Android versions because "setJustificationMode" was introduced until API 26
Light Weighted Scratchcard View Library for Xamarin.Android
Scrollable view which can be used to give different choices to user with nice UI.
SASL client library
Lightweight Android easing library
A view animating between two items for Android, supports multiple switching animations or you can customize your own strategy of animations. And its child view can be reused.
An extended ImageView that can stream MJPEG videos.
An Android SDK that provides a new size unit - ssp (scalable sp). This size unit scales with the screen size based on the sp size unit (for texts). It can help Android developers with supporting multiple screens.