Here is a query that works with SQL 2005 to pull the top 100 slowest queries of a database:

SELECT TOP 100

[Object_Name] = object_name(st.objectid),creation_time, last_execution_time,
total_cpu_time = total_worker_time / 1000,
avg_cpu_time = (total_worker_time / execution_count) / 1000,
min_cpu_time = min_worker_time / 1000,
max_cpu_time = max_worker_time / 1000,
last_cpu_time = last_worker_time / 1000,
total_time_elapsed = total_elapsed_time / 1000 ,
avg_time_elapsed = (total_elapsed_time / execution_count) / 1000,
min_time_elapsed = min_elapsed_time / 1000,
max_time_elapsed = max_elapsed_time / 1000,
avg_physical_reads = total_physical_reads / execution_count,
avg_logical_reads = total_logical_reads / execution_count,
execution_count,
SUBSTRING(st.text, (qs.statement_start_offset/2) + 1,
((CASE statement_end_offset WHEN -1 THEN DATALENGTH(st.text)
ELSE qs.statement_end_offset
END

- qs.statement_start_offset) /2) + 1) as statement_text FROM
sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) st
ORDER BY total_worker_time / execution_count DESC