I recommend, so far, TuSSH. It is not perfect, but it does do SSH2, which the old standby TGSSH does not. I have not used TuSSH a bunch, but it appears adequate, at least for the very low-use I intend.
There are at least two other commercial alternatives, Mocha Telnet (which you can try before you buy–I have not done so yet, so I can't tell you how good or bad it is) and Expand Beyond's PocketAdmin Console, for which a 30 day eval is available. I'll probably get around to trying both at some point–the fact is, I'm willing to pay for a good enough app, but it will have to display significant benefits over TuSSH.