I thought it might be useful for each of us to post the software we consider to be indispensable for our pc so that the rest of the people of the forum get to know it too

Firefox
Mozilla Firefox is a web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. Official versions are distributed under the terms of a proprietary EULA. Firefox had 22.05% of the recorded usage share of web browsers as of March 2009, making it the second most popular browser in terms of current use worldwide, after Internet Explorer.
UTorrent

µTorrent (or uTorrent and commonly abbreviated as "µT" or "uT") is a freeware closed source BitTorrent client by BitTorrent, Inc.. It is available for Microsoft Windows and Mac OS X. Both versions are written in C++. It gets the "µ" in its name from the SI prefix "micro" meaning one one-millionth and it refers to the program's small footprint. The program is designed to use minimal computer resources while offering functionality comparable to larger BitTorrent clients such as Vuze or BitComet.

Combined Community Codec Pack
The Combined Community Codec Pack, more commonly referred to as the CCCP, is a collected archive of codecs (video compression filters) packed for Microsoft Windows, designed originally for the playback of anime fansubs. The CCCP is developed and maintained by members of various fansubbing groups. The name is a pun on the Russian name for the USSR (Союз Советских Социалистических Республик, Soyuz Sovyetskikh Sotsialistichyeskikh Respublik); the Cyrillic name for the USSR is initialized CCCP, however it transliterates to SSSR.
That's it for now, i'll update it as it comes to mind.