MuseScore lets you notate and compose music easily with your keyboard, your mouse, or a MIDI keyboard. You can print beautifully engraved sheet music or export it as PDF or PNG. You can play your score, transpose it, and save it as audio or MIDI file. MuseScore also supports MusicXML to let you share your composition with other scorewriters. MuseScore is often advertised as a cost effective alternative for Sibelius and Finale.
X-Plane is a flight simulator that reads in the geometric shape of any aircraft and then figures out how that aircraft will fly. It does this via an engineering process called "blade element theory", which involves breaking the aircraft down into many small elements and then finding the forces on each little element many times per second. These forces are then converted into accelerations, which are then integrated to velocities and positions. This gives X-Plane the most realistic flight model available for personal computers.
Smuxi is an irssi-inspired, flexible, user-friendly, and cross-platform IRC client for sophisticated users. Smuxi is based on the client-server model: The core application (engine) can be placed onto a server which is connected to the Internet around-the-clock; one or more frontends then connect to the core. This allows the connection to IRC to be kept up even when all frontends have been closed. The combination of screen and irssi served as the example for this architecture. Smuxi also supports the regular single application mode. This behaves like a typical IRC client; it doesn't need separate core management and utilizes a local engine that is used by the local frontend client.
WackoWiki is a small, lightweight, handy, expandable Wiki clone. Its main advantages are a visual (WYSIWYG) editor, an easy installer, full Russian support, many localizations, email notification on changes/comments, several cache levels, design themes (skins) support, XHTML compliance, page rights (ACLs), and page comments.
CK-ERP is an accounting, educational, MRP, ERP, and CRM system that runs on top of multiple middlewares. It comprises 32 modules - Contact Management, Customer Relationship Management, Customer Self Service, Vendor Relationship Management, Material Requirement Planning, Warehouse, Inventory, Service, Accounting Ledger, Bank Reconciliation, Accounts Payable, Accounts Receivable, Purchase Order, Sales Order, Quotation, POS for Cashier, POS for Manager, Human Resources, Staff Self Service, Payroll, Administration, Internationalization, Access Control, Data Import, Teacher, Counsellor, Student, Applicant, Family, Registrar, Edu Administration, and Volunteer Management.