The Rust beta only permits use of stable features, and there's an ongoing effort to limit popular crates to the stable subset. The beta will probably lure in new users who want to start building stuff, and this list is intended to be a helpful source for figuring out what libraries they might use.
- libc - Bindings to common C types and functions. Most any FFI work will need this.
- log - Basic logging.
- regex - Regular expressions, and quite fast.
- rand - Random number generation.
- time - Basic interface to platform date/time functionality.
- rustc-serialize - Rust's legacy serialization library, still widely used until serde matures.
- bitflags - Packs your flags in tight.
- pkg-config - Integrate pkg-config with your Cargo build scripts.
- gcc - Integrate gcc with your Cargo build scripts.
- docopt - An implementation of docopt argument parsing.
- byteorder - Big/little endian interop.
- quickcheck - Automatic property-based testing.
- tempdir - Need tempory directories? Use this.
- assert - More advanced assertions than those provided by Rust.
- uuid - UUIDs.
- toml - Parsing for the TOML configuration format, which is also used by Cargo.
- url - URL parsing.
- encoding - Character encodings other than utf-8.
- capnp - Cap'N'Proto - fast serialization. The schema compiler and the RPC module.
- gl - OpenGL bindings.
- clap - Command line argument parsing.
- leveldb - Embedded database.
- iron - A popular web framework.