KoreanClick provides the following data for free.

Top Site by Domain (2008.04)

No	Domain	Unique Visitor (*1000)	Reach(%)	No	Domain	Unique Visitor (*1000)	Reach(%)
- 1	www.naver.com	31,180	96.68	- 6	www.empas.com	19,024	58.99
- 2	www.daum.net	29,095	90.21	- 7	www.yahoo.co.kr	18,096	56.11
- 3	www.cyworld.com	23,724	73.56	- 8	www.gmarket.co.kr	18,006	55.83
- 4	www.nate.com	23,023	71.39	- 9	www.paran.com	15,709	48.71
- 5	www.auction.co.kr	21,004	65.13	- 10	www.tistory.com	13,861	42.98

News/Media (2008.04)	Game (2008.04)
No Domain Unique Visitor (*1000) Reach(%) 1 www.joins.com 13,357 41.42 2 www.sbs.co.kr 10,443 32.38 3 www.chosun.com 9,607 29.79 4 www.hankooki.com 8,457 26.22 5 www.kbs.co.kr 8,314 25.78	No Application Unique User (*1000) 1 Starcraft 3,585 2 SuddenAttack 2,090 3 Maplestory 1,940 4 CrazyArcade 1,741 5 Pmang 뉴맞고 1,523