Best named modules (meta 4 for the most part) are always in demand. Besides expensive faction and deadspace mods, they're the best fittings new players with low skills can use. They're typically as good or close to as good as T2 equivalents while taking less cpu and/or powergrid which makes them easier to fit than T2. Consequently they're often better for players who can use T2 modules too.
The following is a list of some best named modules that sell well. There are others, these are just some of the most popular ones that I've used and traded myself.
Limited Adaptive Invulnerability Field I
Eutectic Capacitor Charge Array
F-90 Positional Sensor Subroutines
F-90 Positional Signal Amplifier
Faint Epsilon Warp Scrambler I
Limited IMN Microwarpdrive I
Local Hull Conversion Nanofiber Structure I
Phased Muon Sensor Disruptor I
Phased Weapon Navigation Array Generation Extron
Upgraded EM Ward Amplifier I
Arbalest missile launchers (all types but particularly heavy, light and rockets)
Regolithic Shield Extenders (all sizes large, medium and small)
Photonic CPU Enhancer
Fleeting Propulsion Inhibitor I
Faint Warp Disruptor I
My absolute favorite T1 module to trade is Limited Adaptive Invulnerability Field I. I've been trading these since my first week playing and I still trade them now. Plentiful supply, they drop everywhere and are in extremely high demand. Prices can be very spiky with sell orders ranging from extreme lows of under 75k to extreme highs of 2 million plus when someone tries to corner the market.
Someone has been trying to corner the market on all best named modules for a couple weeks now. He's camping and throwing an awful lot of isk at the market trying to dominate sales and keep prices propped up high. As a result all the best named modules are extremely high priced lately.
This means right now is a great time for new players to break into trading best named modules. As the little guy your advantage is you can spend more time concentrating on a smaller area, fewer items and smaller orders than the big guys can. Update and renew your orders frequently and transport stacks of modules to sell on whatever nearby hub has the best sell prices. Buy them cheap in out of the way areas and sell them on main trade hubs and/or major mission hubs. If you do it right you can sell well under his prices, make big profits and easily more than double your money every day until your volume gets large enough to start slowing you down.
For a little market pvp fun I like to put up a 10 or 20 jump buy order for 100 or so just a little over the highest priced 40 jump / regional order. That way I get the close ones and the regional buyer trying to corner the market with massive buy orders gets stuck having to travel 10, 20 or more jumps to pick up all the ones he gets.
One caveat, if you engage in this type of market pvp be aware a smart market manipulator would have amassed huge cheaply purchased stockpiles *before raising prices. Assuming he did, eventually he's going to dump those stockpiles so make sure you don't buy too much at high prices now and get stuck with them when prices go down again. Only buy what you can reasonably expect to sell in a few days.
Please feel free to comment on other best named modules that sell well and I'll add them to the list.