First, you can contribute $5,000 to ira's in 2008 be it a rothira , a traditional ira or some combination of the two. The most you can contribute is a total of $5,000. If your spouse is not covered by a qualified plan(ie a 401(k) you can contribute $5,000 for her as well.(income limits may apply)
SEP ira's and simple iras allow for higher contribution limits.
Also, as a self employed person, if you don't have any employees you can contribute to an idividual 401(k).
more info:
http://personal.fidelity.com/products/retirement/getstart/newacc/keogh.shtml.cvsr?refpr=sb006
see your tax advisor for specific advise.