This is a list of smaller, lesser-known libraries that I've used and vouch for. It has bookmark value for me as much as anything but I'm keeping it here in the hope someone might find it useful.

gistfile1.asciidoc

Libraries

JVM

Retrofit

Strongly-typed Java interfaces for REST endpoints. Supports returning RxJava Observables. Similar to Feign which is by Netflix but doesn’t support Rx.

Jerry

HTML parsing, traversal and manipulation with a jQuery-like API.

Primer

Test double for web services.

JOOQ

Strongly-typed fluent API for SQL queries.

JDBI

SQL API with nice DAO support.

Browser

Semantic.gs

The simplest and for my money best grid system. Supports LESS, Sass and Stylus.

Lettering.js in 128 bytes

Non jQuery dependent version of Lettering.js

Geomicons

Nice geometric icons.

Normalize.scss

Sass port of Normalize.

Transparent Textures

Transparent PNG textures for CSS background-image.