There are several acts named (or formerly named) "Nemesis":

1) An Acoustic/rock/metal band from Sri Lanka formed in 2005.
URL: http://www.myspace.com/nemesislk

2) An Australian act mixing ambient, Industrial, noise and black metal.

3) An early Swedish heavy/speed/doom metal band: They released a few demos and an EP, "The Day of Retribution", before becoming epic doom metal pioneers Candlemass.

4) A Hungarian progressive metal band. They changed their name to Age of Nemesis in order to avoid consusions. They have a couple of albums out, and are one of the best prog metal acts of Hungary. Albums: Nemesis (1998), Abraxas (1999), Eden? (2002), Psychogeist (2006) and Terra Incognita (2007). The latter two are released as AoN already

5) A rock band out of Bangladesh. Nemesis was formed in the winter of 1999. They released their first album, Onneshon, in March 2006. Their members are Maher (guitars), Nondito (Guitars), Zohad (vocals), Yawar (Drums), Ratul (Bass). Their sound is a very clean and controlled kind, with smoothness of the likes of bands like U2. In fact, U2 is a part of most of their live shows, as is Joe Satriani, owing to Maher is who is a brilliant guitar player. More information about them and their music can be found on their website www.nemesisbd.tk

6) A Korean rock group: Ha Se Bin (EVE) was in this group before he joined EVE for EVE's 6th and 7th albums. The drummer for Nemesis is also the support drummer for EVE's 7th album. They are in currently in both bands, although Nemesis is on hiatus.
OHP: http://n-sis.co.kr

7) A Finnish ambient electronic band: Formed in 1987 and has released records on Belgian Antler Subway records as well as on Finnish Spinefarm's Freeride label. The band is currenlty active, releases are distributed through Origo Sound, Synth Music Direct and by Nemesis themselves.
URL: http://www.nettilinja.fi/~ahassine/

8) A Czech power metal band: In 2006 they changed their name to Symphonity.
URL: http://www.symphonity.com

9) A Czech death metal band: They were previously called Aggressor, but later changed their name to Nemesis after a member returned from the military. They were formed in 1989 and are currently active.

10) An American alternative rock band: Previously know as NEMESIS, the band opted to change the name to NEMESIS ARMY to avoid confusion with other acts called Nemesis.

11) An American pop/dance duo: Nemesis includes twin brothers Jacob & Joshua, currently starring in MTV-LOGO's reality show "Nemesis Rising" (named after their forthcoming album). The first single is "Number One In Heaven," which spent several weeks atop the LOGO "Click List" weekly top ten video countdown.

12) A Scottish nationalist rockband.

13) A Polish black metal band from the city Wrocław, formed in 2001. They released two demos: After Dark (2002) and Ruins of Souls (2003). After that the band split up.

14) German folk/pagan black metal http://www.myspace.com/heidenmetall
nemesis-eod.de.vu

15) Greek Progressive rock band of the mid to late 70's/Early eighties.

16) Israeli Nitzchonot/Uplifting Trance project.