Prices for prime real estate in London and New York are down more than 10%, whatever the agents may claim; and that is usually a forward indicator for the rest of the market. Rental income is falling even more swiftly: the latest survey by the New York Times showed declines of up to 20%.

The stockmarket is directionless: a double-dip recession, or extended economic stagnation, is still a likelihood, and company valuations still assume a return to consistent earnings growth. Corporate debt is increasingly risky, as even blue-chip companies flirt with bankruptcy. Money market returns in the US and Europe are at their lowest rate in decades.

So where to invest? Here are some ideas, none of them, it has to be said, based on exhaustive analysis. My rough-and-ready technique: look at current technology trends, and tease out the long-term implications. The market usually focuses on the companies and sectors in the immediate path of change, while the real beneficiaries are often in another business entirely.

The classic example: the invention of the automobile created unexpected opportunities in out-of-town shopping malls. There are modern equivalents: flat-screen technology, the pervasive internet, cheap computer graphics, high-speed wireless networks, discount air travel, and the list goes on. All familiar trends, all with underappreciated corollaries. Time for some lateral thinking.

[1.] Take outdoor advertising. LCD manufacturing has become so efficient that 15-inch screens are standard in larger laptops, and companies such as E-Ink promise further improvements. Within another decade, it will be cost-effective to replace traditional billboards with moving displays, which will be much more attractive to advertisers.

In Steven Spielberg's Minority Report, Tom Cruise runs a gauntlet of personalised video pitches; that is less science fiction than a straightforward extrapolation of the present. Already, high-traffic locations such as Times Square in New York are plastered with dynamic advertising.

The opportunities: outdoor display businesses, such as Viacom Outdoor and JC Decaux; public transport systems, which will extract greater value out of their captive commuter audience; and some real estate, such as the building in which I rent in Manhattan, the costs of which are already funded from the blank wall which faces Houston Street.

[2.] Pretty places. The growth of discount airlines such as JetBlue and easyJet, in the US and Europe, has put smaller destinations within cheap and easy reach of major cities. And the spread of high-speed internet access makes it ever easier to access corporate information systems, and communicate with colleagues, while away from the office. If location no longer matters, why not spend the winter in Marrakech or the Caribbean?

There is nothing new about the holiday home; northern Europeans have been buying second properties on the Costa del Sol for decades. But real estate in warm and pretty places has further to go. The Buzz flight to Bergerac has boosted property prices in that part of the Dordogne; and one can reasonably expect the discount airline network to cover the whole of Europe and the Mediterranean, and north and central America.

My picks, though these are subjective: Essaouira, in Morocco, if they can get an airport built; the resorts outside Tunis; Dubrovnik on the Adriatic; the Buda hills of Budapest; and -- this one I'm seriously exploring myself -- Havana. The Cuban capital is just three hours flight from New York, it beats Miami Beach hands down for allure and excitement, Castro is getting old, and you can buy an Art Deco apartment by the promenade for $20,000.

As for high-speed internet, StarBand now offers a satellite connection for $69.99 per month. The only problem: how to smuggle it into Cuba.

[3.] Another real estate thought: old skyscrapers. Their value as office space fell in the late 20th century, because the ceiling height did not allow sufficient headroom for telecommunications and electrical wiring, among other things. Wi-Fi high-speed wireless connections will give new life to older buildings. Local wireless networks can carry both data and phone traffic. Time to rip out the false ceilings, and raise the rent.

[4.] Online media. I know what you are thinking: we've heard this one before, in 1999, and we all know how that turned out. All the sensible investors have written off the sector: built on hype, margins unprotected by any barriers to entry, of dubious value to advertisers, offering services for which consumers refuse to pay.

Which is precisely why online media is such a good investment now. Valuations are sensible. As broadband access spreads, consumption of online media is growing. For a range of categories, from travel to books, the internet is now the primary means of purchase or research. Online advertising, despite reports of its demise, is booming: web search alone will generate an estimated $1.4bn in revenues in 2002, up from $400m in 2000.

And the costs are way down. No longer is it necessary to hire an army in the anticipation of hypergrowth, and a stockmarket flotation. The software is vastly cheaper: for a small media site, Movable Type provides all the features a publisher needs, for $150; Vignette used to gouge credulous publishers for millions. Finally, marketing: there are so few new media ventures that attention can be bought more cheaply than the $30,000 a month of a basic public relations retainer during the boom.

The only problem: there are few public companies standing in which to invest. AOL TimeWarner is too much of a mess, Yahoo is a pure-play online media investment, but its premium services strategy is yet to be proven; and Google will be extravagantly priced when it comes to market. The better opportunities are in private equity, buying underappreciated assets such as Slashdot, or in online media startups, which is where I am putting my own energy.

[5.] Telecoms. One short recommendation: incumbent telecom companies. Yes, their stock prices are already corrected, and they appear reasonably priced on a price-earnings basis. But the market does not sufficiently appreciate that competition is about to intrude on the last bastion of the telecom giants: the local phone business.

I have just installed a box by a company called Vonage, which plugs into my cable internet connection, and provides normal phone service, and unlimited national and local calls in the US, for $39.99 per month. Voice over the internet, which was an amusing but unusable curiosity, is now good enough.

Add in the high-speed wireless networks -- often free to access -- which are spontaneously springing up all over major cities in the US. I would not be surprised if regional phone companies such as Verizon go out of business over the next decade.

[6.] If all these ideas seem speculative, as they should, one final suggestion: cash. In a deflationary environment, higher returns are often illusory. Even if interest rates are vanishingly low, real estate prices can still fall, as they have in Japan. Preservation of capital, rather than reliably high returns, should be the goal. Were you an investor in Japan over the last decade, better to have stayed in cash. After all, if you buy into the prediction of deflation, the assets will only get cheaper.