hi cosmo-torun,
There's a CAMK workshop *this* week: 12-17 July 2011: Cosmic web morphology and topology http://users.camk.edu.pl/pchela/workshop/
Here, "topology" means 2D topology of constant density surfaces embeded in 3D space, not 3D topology of 3D spaces.
This is about the cosmic web, meaning the filaments and knots of mostly dark matter and some baryonic matter on scales of about 10-100 Mpc. Most of you have seen the animation of a simulation of this that i show fairly often.
Observations of the cosmic web include clusters at the "knots" of the web (e.g. observed by OCRA through the SZ effect) and the Lyman-alpha forest - clouds of neutral hydrogen that absorb background quasars.
i don't expect any problem with informal participation, but send an email to Wojtek Hellwing (see the website) to briefly introduce yourself. You can make a day trip to Warsaw - leave early morning and return e.g. with the 18.45+(n>1 * 10 minutes) train - or stay overnight at a friend's place and see several days of talks. The talks look mostly (but not only) theoretical to me, and based on the FLRW model + perturbations, not the inhomogeneous approach. This is an easy opportunity to meet some international extragalacticians/cosmologists.
pozdr boud