I seem to have settled into a reasonable work flow with my photography and Lightroom.
I have multiple memory cards for each camera. Two 2 gb cards for the Canon SD700 IS - shooting jpeg gives me about 700 photos per card or about 15 min. of video at the highest quality (640x480, 30fps). I can't remember the last time I filled up one of these cards. I have four 4 gb cards for the Pentax K10D - shooting DNG (raw) I get about 240 photos per card and I do fill these up sometimes. For the Pentax I always carry at least one spare memory card and a spare battery.
I have spare batteries for both cameras but seldom need them. The last a long time and most of the time it's easy to recharge them. The exception is in more remote locations where power isn't readily available.
When traveling I usually download/import once a day to Lightroom on my MacBook. I take advantage of Lightroom's option to make a backup as it imports, to an external hard drive. I also have Lightroom set to back up its catalog to the external drive daily. When I fly I keep the MacBook and the external drive separate to improve my chances of not losing both!
I also separate the cameras (and their chargers and other accessories) so even if one bag gets lost I'll still have a usable camera. I worry as much about the chargers since they'd be impossible to replace in most places and without them the camera would soon become useless. In this respect I like the use of standard AA batteries in my Canon S3. I still use rechargeables but I can use readily available disposables in an emergency, and there's also a much better chance of replacing AA rechargeables and recharger.
After I download I do NOT erase the memory cards and I rotate them so I put in the least recently used card. That way the cards provide a third short term backup in case I mess up an import. I erase a card when I put it into the camera. The only drawback to this system is that occasionally I forget to erase the card when I put it in the camera. I then run out of space soon after I start shooting, but I can't erase the card at this point because I've put new pictures on it. At least Lightroom has an option to ignore already imported photos.
My primary Lightroom catalog and photos are on my desktop system at home. For each trip I start a new catalog on the MacBook just for that trip. When I get home I import that catalog into my main system. One minor drawback of this is that I start fresh with keyword tags and sometimes they don't match with the ones I'm using in my main catalog. But this is minor and easily fixed using Lightroom's ability to rename keyword tags.
I keep both the main and the MacBook catalog organized primarily by date with the yyyy/yyyy-mm-dd format. I rename as I import to yyyymmdd - filename. When I first starting using Lightroom I didn't rename but the straight camera generated file names aren't very helpful, and there's always the risk of duplicates. In my main catalog I add another level of folders for major trips e.g. 2008/2008 Baja/yyyy-mm-dd. This makes it easier to select all the photos for a trip e.g. to put together a slide show.
Some people keep their photos in folders by subject or type rather than date. To me recording subject or type is better done using tags. Otherwise you're continually faced with questions like which folder do I put a picture of a bird on a beach at sunset? In birds, beaches, or sunsets? That's the power of the ability to apply multiple tags, in this case birds, beaches, and sunsets. And it's just as easy to click on a birds tag as it is to click on a birds folder. Of course, this assumes you're inside Lightroom. Outside Lightroom you'd have no easy way to select the birds tag.
I'm not very systematic about my tagging. I'll do a little tagging when I first look at the photos. And I might go through and apply a tag (e.g. birds) if I want to make a selection of a certain type or subject. But lots of my photos aren't tagged at all, which makes it hard to find them later. I could do better in this area.
Another choice is whether to delete "bad" pictures e.g. badly exposed or out of focus. Personally, I don't delete, no matter how bad the photo is. I just flag it as "Rejected" and normally I filter rejected photos out of view. This is similar to Gmail's philosophy of keeping everything. Storage is cheap. It's not so much that you'll ever want a totally ruined photo, it's the time and mental effort needed to decide on the marginal cases. You can always change your mind about a Rejected photo, if you delete it, it's gone.
One case where I might be tempted to delete is when I'm bracketing exposures. Since they're more or less duplicates, why not just keep the best exposure? But again, it's not always clear which is "best". You might actually want to combine several exposures for a HDR image. And Lightroom's ability to "stack" photos avoids having to look at the "duplicates" most of the time.
I'm finding the K10D tends to overexpose bright scenes like snow or sand. I need to figure out when I need to override the exposure, by how much, and what the best way to do that is. I've been bracketing when I suspect there will be a problem. So far it looks like -1 stop does the trick. Lightroom's Recovery slider (and shooting raw) lets you fix a certain amount of overexposure, but it can't recover what really isn't there. This is where composing in the display in the small camera helps. I need to get in the habit of reviewing photos on the K10 and maybe even checking the histogram. Of course, that only works for static subjects where you have the option of another shot.
I also find that for certain shots e.g. closeups I need to manually focus the K10, especially when low light means a small depth of focus. The auto-focus is pretty good, but it can't read your mind and doesn't always pick the right thing to focus on.
On my main system I use Chronosync to automatically back up my photos and catalog to a network drive. And I also have TimeMachine running to an external drive. But currently I don't have a good offsite backup system. I keep a lot of my photos on my work computer, but I don't have a convenient (or automatic) way to do this so it's not too reliable. I've tried a few ways to sync my home and work computers (especially my photos and music), but it hasn't been too successful, partly because of the sheer volume of data to sync, especially at the start. An online internet backup is another option, but again, it's tough with the volume of data, again especially at the start. And not just at the start - when I come back from this trip I'll be adding 40 gb in one shot. That's a lot to transfer over the internet.
When traveling, I try to upload photos to the web every few days so my family and friends can keep up with me. So far I've been using Google Picasa Web Albums. Before Lightroom I was using Picassa to organize my photos, so it was natural to use it's web albums. It works well enough so I've just kept using it. And the Lightroom plugin to export directly to a web album makes it very easy. Now I keep thinking I should give Flickr a try.
I do a certain amount of tweaking of the photos I choose to post - mostly cropping and exposure. For this, and for general organizing, it's great to use the same software (Lightroom) traveling as well as at home.
You can check out some of the photos I've posted at : http://picasaweb.google.com/apmckinlay