Mobile Terminal 426 appears to be the only non-crashing iOS4 Terminal App. Unfortunately it's missing all of its convenience features, like gestures. Are there alternatives?
I use iSSH: http://www.zinger-soft.com/iSSH_features.html It's available on the app store, but if you're jailbroken you can ssh to 127.0.0.1 and it works just fine. Costs $10 though.
If by terminal you mean SSH (or telnet): I have used TouchTerm (from way back when it was for free, now its 4$) and iSSH.
I like TouchTerm better on the iPhone as I find the semi-transparent keyboard better.
I prefer iSSH on the iPad because it has a real iPad version.
Also iSSH has a VNC client and an X server that can be tunneled over SSH. But its 10$.