About GeoGebra:

1. International GeoGebra Institute (IGI) www.geogebra.org/igi
2. Official website GeoGebra www.geogebra.org/
3. GeoGebra Institutes www.geogebra.org/cms/institutes
4. Events www.geogebra.org/cms/events
5. GeoGebraTube www.geogebratube.org/
6. GeoGebraWiki wiki.geogebra.org/en/

The next few site constitute a rich database of information related with GeoGebra:

http://mathandmultimedia.com/geogebra/

http://giohio.pbworks.com/w/page/7469379/FrontPage

http://school-maths.com/geogebra_institute/   

http://www.dl.bsu.by/course/view.php?id=426

http://www.uni-miskolc.hu/evml/geogebra/  (HU)

http://www.geogebra.fi/  (FI)

http://www.emathforall.com/ss/index.html?Constructs  (MK)

http://domovchiyska.schools.officelive.com/default.aspx  (BG)

http://elishapeterson.wikidot.com/technotes:geogebra-cobwebs   (EN)

http://webspace.ship.edu/msrenault/   (EN)

http://notropis.net/geogebra/index.html   (EN)

http://geogebrawiki.wikispaces.com/Home  (EN)

http://prairiestate.edu/skifowit/geo/index.htm  (EN)

http://school-maths.com/   (EN)

http://www.gcsemathstutor.com/index.php  (EN)

http://media.lanecc.edu/users/gettyst/   (EN)

http://maine.edc.org/mod/resource/view.php?id=375   (EN)

http://www3.ul.ie/evlm/   (UK/BG/FI/HU/ES/SK)

http://geo-bra.blogspot.com/   (BG)

http://mathandmultimedia.com/geogebra/   (EN)

Others:

1.   "Angel Kanchev" University of Ruse www.uni-ruse.bg  (BG/EN)

2.   Ministry of Education, Youth and Science  http://mon.bg    (BG)

3.   Bulgarian Academy of Science http://www.bas.bg/  (BG/EN)

4.   Bulgarian Academy of Science, Institute of Mathematics and Informatics  http://www.math.bas.bg/index.html/    (BG/EN)

5.   Fibonacci - Disseminating Inquiry - Based Science and  Mathematics Education in Europe http://www.math.bas.bg/omi/Fibonacci/index.htm   (BG)

6.   InnoMathEd - Inovations in  Mathematics Education on European Level  http://www.math.bas.bg/omi/InnoMathEd/  (BG)

7.   Union of Bulgarian Mathematicions  http://www.math.bas.bg/smb/  (BG) 

8.   Union of Scientists in Bulgaria  

http://www.usb-bg.org/Bg/index_bg.htm  (BG), 

http://www.usb-bg.org/English/english.htm  (EN)