Sparse is a semantic parser of source files. It's neither a compiler (although it could be used as a front-end for one) nor a preprocessor (although it contains a preprocessing phase). It is meant to be a small, simple, easy to use library. Its function is to create a semantic parse tree for some arbitrary user for further analysis. It's not a tokenizer, nor is it a generic context-free parser. Context (semantics) is what it's all about: figuring out not just what the grouping of tokens are, but what the types are that the grouping implies.
The spasm anti-spam milter is a spam filter for sendmail 8.12+ (with libmilter support). Its current features include logging and quarantining of rejected spam, fully virtualised settings for domains, individual whitelists and blacklists, and over two dozen filters, which can be set individually on a per-domain or per-email address basis, including local (system) blacklist, rDNS resolution, HELO/EHLO verification, envelope sender address verification, numerous DNS-based lists, whitelist-only mode, and auto-blacklisting via spamtrap addresses and unknown user rejections.
specter is a user-space logging facility for the Linux netfilter system. It uses netfilter's ULOG target to gather packets, and passes them to attached plugins. Its features a flexible and robust modularized structure, and is based on ulogd, but has improved design and wider functionality. It currently supports a basic set of network protocols (IP, TCP. UDP, and HTTP) and can save data as text or PCAP, or add it to MySQL or PostgreSQL databases.
spectrwm is a minimalistic tiling window manager that tries to stay out of the way so that valuable screen real estate can be used for much more important stuff. It has sane defaults and does not require one to learn a language to do any configuration. It was written by hackers for hackers and it strives to be small, compact, and fast.