There are tons of great charging gadgets out there (see my brief RichardSolo review here and a more in-depth one by Louis here), but the Mophie juice pack line of products for iPhone/iPod give a lot of charging bang for the buck. If you are interested in keeping your iPhone or iPod topped up with smart battery technology, then you might want to give the reserve a try. It's "almost" keychain-sized and sports a retractable Apple connector built into the unit.
As a small carry-along charger for my touch, the reserve is perfect. Because it also uses miniUSB (for recharging itself), I can literally go wih one cable. One thing I both like and dislike about the RS 1800 is the universal charging aspect, mainly because it comes at the expense of extra cables you must lug around (or lose or forget to pack). The reserve is about 2/3rd the size of the 1800, but the 2 are comparable in weight.
The mophie reserve comes in a little small product container, the contents of which include the charger itself, a USB cable, and a small instruction manual. The product hype page here says the reserve is the first charging device to use a retractable connector design (could be, but might be hard to verify that). The Apple connector interface has been around for awhile now, and I would be surprised that the idea has not been used before (unless mophie owns patents on it). The device can potentially charge your device using half the juice of typical batteries. The reserve uses an advanced Li-Poly 1000mAh battery design.
In a quick comparison of features to the RS 1800 (also Li-Poly), though, the 1800 has a lot of extra tricks up it's sleeve. One is the fact that pass-through charging is supported. You can connect a device and plug the 1800 in at the same time. Actually, it simply tops up your device before restoring it's own battery, but the juice pack can either charge or be charged. Not both (even serially). While the reserve has a small built-in flashlight like the 1800, it has no laser pointer and it also lacks a miniUSB output (being iPhone/iPod targeted, obviously it doesn't need it). Also, of course at 1800 mAh, the RichardSolo charger has more capacity.
The juice pack reserve has a few nice tricks of it's own. It charged my iPod fast, and does not need to be turned on or off. It detects when a device is connected, charges and turns off at disconnect. You can quickly check the charge level with the push of a button (which you can only do with the 1800 when plugged in). I already mentioned the retractable connector, which could be a bit longer--I have to remove my case to get it to fit snugly against my iPod. The reserve is compatible with all iPod and iPhone models.
I would have to say it is a toss-up as to which one I prefer, but the mophie reserve is slightly more travel friendly. It needs only a single accessory cable, and is fast on top-up and recharge. It's also smaller, and cheaper than the 1800, and can be attached to your keychain (though it is on the largish side for that). On the other side, the 1800 is more universal, has more features, and also has more capacity. It also comes with some useful charging attachments (car and wall socket, etc.). The Mophie product page claims you get 500 or so discharge cycles out of the reserve, which will probably keep it usable for years (results will vary, I'm sure). I have always gotten long life out of my rechargeable gadgets by keeping them regularly topped up, and not leaving them fully discharged for long periods of time. I will have to let you be the judge on which battery pack is better, but I recommend either. You can check out the product page for the mophie juice pack reserve here. It retails for $39.95...