Here is a list of links to lists of
hotspots. If you do a search, you'll also find a few others people have posted over the past couple of weeks.
First, I generally suggest people look at cards other than Dell's TrueMobile. Many people complained early on with the X5 that the range was very poor with that card. Based on some recent posts, the latest drivers for the card with WM03 may have taken care of the range problems but if you keep an eye on the 'deals' forums, you'll probably find cards that are just as good for much less. I've seen Linksys, D-Link and Ambicom WiFi cards for <$30.
If you want the card that's considered the best, look for the Socket Low Power WiFi card. It's also the most expensive but there is a similar card made by Symbol (possibly the same card just rebranded) which you can find for much less - also in the $30 range.
As for Internet service away from home, it depends. Many of the available hotspots do charge for the connection (T-mobile at Starbucks & Borders bookstores are the most famous for-fee WiFi but there are also Boingo and Wayport sites at many hotels and airports). These offer connections by the hour, by the day or on a monthly subscription rate. If you travel to the same or a few locations frequently, it would probably be worth a little research into which services might be available to you.
Your other option might be to check into a service through your cell phone service. With the right phone, you can connect that way and not be limited to needing to find hotspots.
Check out the WiFi FAQ linked from my signature for some more wireless answers.