Personal Experiences,Study, Learning Blog of Abu Rashid aka Harun

Libreoffice
Good one and free open source software. It has all functionalities like MS Office including word,excel,powerpoint.

Irfanview
a small but powerful image editing software

KM player
plays almost all format of audio and video

dopdf
converts word to pdf and its a very small software.

wordweb
nice English to English dictionary

Some more suggestions on free useful software could be found here:
http://www.moneysavingexpert.com/shopping/free-office-software