Under settings > internet connections there are 3 options, they should be as follows:

Connect automatically - Any Connection
Search Interval - (Any except for 'Never)
Switch to WLAN when available - ticked (set to yes)

This should give you what you want, if not, something dodgey might be going on.

Ignore most of the comments here. I am always on wifi or 3G as well. It should connect automatically given your settings. Perhaps your data signal cuts out a lot? If it gets disconnected it will wait a few minutes before trying to connect again. You could try decreasing that time in the network settings, but it will cause battery drain in poor signal areas.

Some (all?) of the builtin programs auto connects when needed (at least the browser and app manager does so IIRC). However I can't think of any 3rd party apps auto connecting - fennec and faster app manager certainly doesn't.

For a "mobile computer" the internet connection handling sure sucks. And Nokia sure sucks always taking 1 step forward and 2 steps back:

The E70 had a connection groups feature, each connection group consists of 2 or more internet connections which will be tried in order of preference. Then in each program you could specify whether to ask which connection to use each time or you could specify auto use a connection group or an individual connection. This worked, mostly. But with the E71 this concept of connection groups was removed !!!???!!!

I never have connection issues and my settings are like James_Littler laid out.

I am always on at least 3G, unless I get within a wireless device that my phone can connect to (either a previous setup encrypted connection or an open wifi hotspot).

That is actually the point of the settings James talks about I believe. If you want the apps to be asking you if it can access the internet than you'll choose the selection "Always Ask" under the "Connect Automatically" setting.. I have my search interval set to 10 minutes.

I don't want to be asked, I just want it to get a connection whenever any program needs one. I already have it set to:
Connect automatically: WLAN
Search interval: 60 minutes
Switch to WLAN when available is enabled.

Like I said none of the 3rd party programs I use auto gets a connection.

ok, i did some more testing last night. i turned off the auto-disconnect app i'd been using (which successfully dropped the connection down to 2G from 3G, but i was having the data connection problems described above), phone was set to 'GSM' all night, hopped on the train, went off to dinner at a friend's place, then a few drinks outside a bar.

no access to wifi during that time, and the phone stayed on 3G (or 3.5G as it found it) for the duration. each time i went to use the phone itself, data was immediately available (didn't experience any of the 'no data connection available' prompts i described earlier).

so, everything worked as i'd expect under this scenario, but, also as expected, battery life was an issue. during the six hours or so, the battery was completely drained. was reading e-mails during this time, couple of IMs, checked train schedules and listened to music on the train ride & walk home from the station.

i apologize for referencing the iphone, but this is my previous experience... so, when i used the iphone, leaving 3G on was also not a feasible possibility (edit: from the standpoint of battery life, i mean... battery would run flat in way less than a day). i would turn 3G on when i needed to use the net away from wifi, and switch back to 2G when the phone went back in my pocket. this is the basic functionality i'm looking for with the N900 as well... without losing my data access or making it overly cumbersome to pull the phone out and quickly run an app that needs a data connection.

i guess what i'm looking for is a simple switch to turn off the 3G functionality, so that i can maintain a data connection over the slow but efficient (from a battery standpoint) 2G connection. i would have done this last night, but the phone was set to 'GSM' not '3G' yet stayed in 3G all night. is there a simple toggle available? what would setting to 'dual' accomplish, relative to the above?

http://maemo.org/packages/view/3g2g-...ection-applet/

Just and idea: I think that it´s possible to make 2g/3g selection to work with lock/proximity sensor. It probably means that you have to learn how to control system from terminal. Probably queen beecon might have some scripts/examples in wiki.