Here is a Arduino Boot loader for ATMega8 with about 2 Second Reset Timeout ( Since all boards now support autoreset ) . Well the source code comes with arduino but you have to use a gcc < 4.0 to get it compiled under 1 KB.
Some how i found it a headache to compile under windows , so here is the compiled version so that you dont have to go though that.
So you can just download here …
External Crystal 16 Mhz , 2 Second Timeout with 19200 as Baud.