I haven't written very much, but here are a few things. Not all are online, but please email me if you would like a copy of something.

• Basic notions in mathematics. Some lecture notes for a course I gave in 2006 on sets, elementary number theory, and some abstract algebra.
• Harmonic analysis on number fields. Covers Tate's thesis, together with background material. This was my MSc thesis at KTH, Stockholm, in 2005.
• Introduction to etale cohomology. My Part III essay, Cambridge, 2006. Written under a lot of stress, I am not very happy with the result, but perhaps it could be useful for someone. In my view, the only reference making etale cohomology understandable is the book of Tamme.
• An old draft (2007), outlining some questions on cohomology theories.
• Since December 2008, I have a blog