Microsoft Visio vs Dia

Dia is a open source software that inspired by the commercial Windows program 'Visio', though more geared towards informal diagrams for casual use. It can be used to draw many different kinds of diagrams. It currently has special objects to help draw entity relationship diagrams, UML diagrams, flowcharts, network diagrams, and many other diagrams. It is also possible to add support for new shapes by writing simple XML files, using a subset of SVG to draw the shape.

It can load and save diagrams to a custom XML format (gzipped by default, to save space), can export diagrams to a number of formats, including EPS, SVG, XFIG, WMF and PNG, and can print diagrams (including ones that span multiple pages).

Download
http://www.gnome.org/projects/dia/downld.html

Nero burning rom vs K3B

K3b is an open source application for creating/burning CDs and DVDs. Features include CD and DVD ripping with DivX/XviD encoding, DVD copy, ISO burning, Video CD (VCD) creation, Audio CD creation for almost any audio file, CD-TEXT support for audio CDs, support for DVD-RW and DVD+RW and much more. On top of all this K3b has a great user interface which make it simple to use.

Download
http://k3b.plainblack.com/download

Microsoft Exchange vs Zimbra Collaboration Suite

Zimbra is the leader in open source, next-generation collaboration and messaging software.

We provide innovative experiences to end-users and their administrators because we see existing tools are fundamentally broken. We also believe in compatibility with existing infrastructure and applications (both open source and proprietary). Thus our solutions are cross-platform: including Linux and Mac OS X on the server-side; Windows, Linux and Mac on the desktop; and Firefox, Safari and Internet Explorer browsers.

Key customers we work with include service providers, higher education institutions, and Fortune 1000 enterprises, particularly in the financial services, retail, and manufacturing sectors.

Download
http://www.zimbra.com/community/downloads.html

Microsoft Active Directory : Fedora Directory Server

The enterprise-class Open Source Software LDAP server for Linux. It is hardened by real-world use, is full-featured, supports multi-master replication, and already handles many of the largest LDAP deployments in the world. The Fedora Directory Server can be downloaded for free and set up in less than an hour using the graphical console.

Download
http://directory.fedoraproject.org/wiki/Download