If you are still lacking some experience (i.e. training), you might want to ask your voice instructors for some arias that would be suitable for you current abilities and voice. Something too easy might not challenge you and something too hard would only frustrate you and maybe cause some vocal strain.
Now that I've posted my "disclaimer"--Del gave you several great arias. Mozart wrote a lot of big opera roles for bass and bass-baritones--more than he did for tenors. However, nothing beats Russians when it comes to music written for basses. Beside the Eugene Onegin, try these--see if your music department might have this collection handy. (Look in the library---plus if this gives you any ideas, you can track down the sheet music by individual arias or by operas). The lyrics are in Russian, transliterated Russian, and English lyric version.
http://www.sheetmusicplus.com/title/Russian-Operatic-Arias-for-Bass/7431277
And I like this Handel aria for bass because it's fun. It gives basses a chance to show off some flexibility usually thought limited to only sopranos and tenors.
http://www.youtube.com/watch?v=WTjksYe2KvI
http://artsongcentral.com/2008/handel-i-rage-i-melt-i-burn-o-ruddier-than-the-cherry/
There are quite a few Handel arias (both from operas and oratorios) that you may want to try, but they aren't necessarily always sung by basses. Sometimes they are sung by baritones, bass-baritones, and even countertenors and female singers (an octave up or more).
For example--"Or La Tromba" from Handel's "Rinaldo"
http://www.youtube.com/watch?v=oaNR30akiUs
http://www.youtube.com/watch?v=mUcfWx7uh9k&feature=related
Also from "Rinaldo"
Sibillar gli angui d'Aletto
http://www.youtube.com/watch?v=LMDPM5NzNYk
Both "Why Do the Nations?" and "The People That Walked in Darkness" from "Messiah" are other good bass arias that you might try. Don't ignore other classical vocal works like oratorios and art songs. Art songs are a good way to expand your performance and singing skills, and have an added advantage that you can pick your own key while you are usually expected to sing arias in whatever key they are written (there are exceptions--some arias will be transposed for recital material or for use in voice training).