Crewe DMD has around 6xClass 56s visble from the station with a few extra at the back of the depot. There is one 58 round the back although all the 60s and 56037 are kept inside the DMD. There is also a couple of 47s hidden round the back of the depot and two 47s (47796 and 47847) shunt at the depot.
There isn't a huge amount visble at Crewe IEMD, a few 08s, 90s and 92s are visble by the sounds of the last report I heard.
There is also Crewe Gresty Bridge which you can ID a bit from the depot entrance. While Crewe LNWR and Crewe Basford Hall are visble from a field but two ID locos you would need binoculars.
You can see bits of Gresty Bridge and Crewe DMD from Shrewsbury to Crewe trains, Crewe IEMD from Chester-Crewe trains, and Crewe Basford Hall and Crewe LNWR from Crewe to Stafford trains.
Hope this helps, Sam
(my avatar is of 47847 shunting at Crewe last week 23/07/12)