As the new rules of the Eurovision postulated a couple of years ago, all the countries should participate in a semi-final. Except for the host country and the Big Four. On Friday, 7 February, the EBU drew the semi-final allocation, the distribution of votes of the big 4 and Norway, and the respective halves (first / second) in which the countries will compete.
By the way, tickets are on sale as of today 
Here are the two lists:
Semi-Final 1 – 25 May 2010
First half:
Bosnia & Herzegovina
Estonia
Finland
Latvia
Moldova
Russia
Serbia
Slovakia
Second half:
Albania
Belarus
Belgium
FYR Macedonia
Greece
Iceland
Malta
Poland
Portugal
Semi-Final 2 – 27 May 2010
First half:
Armenia
Azerbaijan
Denmark
Israel
Lithuania
Sweden
Switzerland
Ukraine
Second half:
Bulgaria
Croatia
Cyprus
Georgia
Ireland
The Netherlands
Romania
Slovenia
Turkey
Here is the allocation of the voting of the Big Four and the host country:
First Semi-Final: Germany and Spain
Second Semi-Final: Norway, UK, France