FastEthernet is still more than capable to handle most things, what you got to remember is that a lot of people who are using these in their sites for things like leased lines, have like 10mb/20mb/30mb leased lines which these types of routers will handle fine.
Anyone who use any bigger links will generally be using the enterprise routers with gigabit Ethernet ports, faster processing, which will mean a fan will most likely be used ala the 2800 series - I configured a 2800 series the other day, beast of a router for a quad bonded ADSL connection set-up.
Unfortunately when you are talking Cisco, things dont come cheap especially if you want the latest lines with the latest features.
I have 3 x Cisco 1721's at home with K9 firmware for learning, using the built in F/E port and an added F/E WIC card to give me 2 x F/E ports on each router - I got these from work but they cost peanuts on ebay, think I seen them going for like £20 each.
Old routers but do the job of learning nicely.
Just going to our stock room to see if I can spot anything else which may be of use to use, although I think the others we have all have fans.
EDIT: yep I was right, we have a pile of 2800 series enterprise routers, Cisco 2600 Series, Cisco 1841 which are fanless and have 2 x F/E ports, Cisco 881 which I think are fanless and has 4 x F/E ports, few Cisco 857's, Cisco 1721's which have a very small fan but very quiet.