At this moment I would not recommend you to go to Serbia. There are epidemics starting to show after catastrophic floods there. I know there was no news coverage about this outside of the former Yugoslav countries. The talk now is about 1.000 year flood not hundred year flood anymore. The Countries that helped in rescue efforts I know off are: Russia, Bolgaria, Belarus, Croatia, Kosovo, Montenegro, Slovenia and others. Unfornately almost no help from Western Europe which is not good.
If you can, send help over Red Cross or Caritas in form of shoes, clothes, dippers, food, disenfectants, antifly sprays, showels, brooms, soda bicarbona and such since more than 1/3 of Serbia has been under water since the catastrophic floods last week. The City of Obrenovac has been basically destroyed and won't be fitt for living for a long time. Some areas of the country probably won't be livable again. The same goes for Bosnia and Hercegovina where several regions with cities and villages don't exist anymore. The biggest problem there represent minefields left from the Yugoslav succession war which have moved and have to be found again. In the minefields there were over 10.000 mines left. Also Bosnia has been bankrupt before this crisis so any financial help is also needed.
The whole region that was covered with water at the floods peak is calculated at approximately 22.900 km2 - Bosnia and Hercegovina + Serbia. That is bigger then the size of my country - namely Slovenia.
One Croatian are was also affected by floods and one City had to be fully evacuated.
If anybody wants to help Serbia financially here you can donate to the Serbian flood relief fund:
http://www.floodrelief.gov.rs/eng/
Paypal Caritas Bosnia: Pay Pal: suzanab21@gmail.com
You can check that the paypal address is genuine on the Bosnian Caritas site:
http://www.carbkbih.org/
Financial donations link for Croatia:
http://blogs.lse.ac.uk/lsee/files/2014/05/CroatiaFloods.jpg