Hi,
You can try basic codes like counters,shift registers,flip-flops.These codes are synthesizable in xilinx.For that you can browse these codes in internet either in VHDL or verilog.
i cannot take simple programs...its for T.E project...has to be somethin like 32 BIT ALU ..or vending machine...voting machine...suggest something other than this becoz this is already taken by sum1