As for any programming language, Ada comes with extensive libraries to accomplish various tasks. Here are some pointers to some of them, although searching on github will lead some more.
The Ada runtime itself, distributed will all compilers, includes an extensive set of packages and annexes, ranging from data structures and containers, to input/output, string manipulation, time manipulation, files, numeric computations, multi-tasking, command line switches, random numbers,...
The GNAT compiler comes with its own extended runtime, with new packages in the GNAT
hierarchy, that provide support for regular expressions, sorting, searching, unicode, CRC, time input/output, ...
gnatcoll is a library that is available from AdaCore's libre site, and includes an extensive logging framework, extending applications with python, mmap, an extensive framework to interface with file systems, parsing email messages and mailboxes, an extensive framework to interact with databases in a type-safe manner, interface to various libraries like icon, readline, terminal colors, support for reference counted types for automatic memory management, JSON files,...
XML/Ada is a library to parse and validate XML documents
GtkAda is a full binding to the gtk+ library, that let's you write portable user interfaces on Unix, Windows and OSX.
AWS is a framework to create web servers in Ada, with full support for various protocols like HTTP, Websockets,... and its own template system.