If your employer has a 403(b) plan then it is a Non-Profit company or an educational institution. If you remove the concept of an employer match, then you in effect have an IRA with the exception of being able to contribute more to a 401(K) & 403(B) plan than you can to an IRA on an annual basis.
If you leave your current job with the 403(B) plan and your new company has a 401(K) plan you can enroll in right away, you might be better off rolling those funds into an IRA. Then, at your new job, just take part in their plan and continue to grow your retirement. Your IRA will be there growing tax-deferred, you can contribute to it (up to a max of $5000 for 1997 plus another $1000 if you are over 50 years old) and you can allocate it any way you wish.
Here's a link to a FAQ page that has some good info;
http://www.403bwise.com/faqs/index.htmlAlso check out the IRS website for particular rules pertaining to the 2006 tax year at;
www.irs.gov
Their search engine is pretty good, just type in what you want to know and it will give you the publications pertinent to your question and links to them in .pdf format.