(CCNA people) A good emulator for router config?

[Ragnarok]

  I'm looking for a good emulation program to practice router and network configurations and commands.  I'm in Cisco semester 2 and we've starting configuring routers now but school access isn't always convenient for practice.  If I can find a good emulator program it would make remembering all this shit easier.  I think there is one on the Cisco site but apparently there are better.  Packet Trace was another one suggested to me. 

Any suggestions?

EDIT: Subnetting is fun.

[Knightshade Dragon]

  I'm looking for a good emulation program to practice router and network configurations and commands.  I'm in Cisco semester 2 and we've starting configuring routers now but school access isn't always convenient for practice.  If I can find a good emulator program it would make remembering all this shit easier.  I think there is one on the Cisco site but apparently there are better.  Packet Trace was another one suggested to me. 

Any suggestions?

EDIT: Subnetting is fun.

I can subnet in my sleep.  As for the sim I like Boson for those.

[Zimix]

The following is the best Cisco Simulator that you will find.  It does require a Cisco IOS image to run.

Cisco Simulator - http://www.ipflow.utc.fr/index.php/Cisco_7200_Simulator
Author's Blog - http://www.ipflow.utc.fr/blog/
Forums - http://7200emu.hacki.at/

Here is an image of what I am currently running in my lab.  It consists of 4 7206s and 2 3640s.  I was testing migration from Sprint's MPLS network (using EIGRP as my routing protocol) to AT&T's MPLS network (using BGP).  All routers and switches are emulated within a VMWare session on one of my machines at home.

[faide]

I second Zimix's link.  That emulator rocks.  Definitely do a lot of labs as your studying for the CCNA it will really help.