If you are ISV or by any reason limited by budget you are probably looking for a free/open source libraries for your development. There are plenty of them amd it’s hard to know which are white and which are black 🙂
So based on my experience I can provide following list for must have from free libraries:
- Jedi JCL – quite big and of high quality library provides you with a lot of reusable routines;
- Jedi VCL – a tons of different purpose visual and non-visual components (also very high quality code);
- Spring4D – a must have library for general development (nullable types, interfaced lists, maps, dictionaries etc.);
- DSharp – aspect oriented programming, mocks for unit tests, logging;
- DUnitX – also integrated in the recent versions of Delphi for the best unit testing;
- LockBox – symmetric and asymmetric ciphers as well as hashes support;
- FastMM – for extended memory leak tracking.
Pascal Today 
I like JCL and JVCL but the trouble is JVCL depends on JCL and installing the latter creates a huge dependency chain in your application. Its easy to add and nearly impossible to remove it from your app. Beware.
Warren
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