Welcome to FlyerTalk.
I have found that one good use for small amounts of 'orphaned' airline miles is for magazine subscriptions. For 300-500 miles, you can get a year's subscription to your favorite magazine. Check the airlines' websites carefully for info on this or call their loyalty program service centers for help. I just obtained subscriptions to National Geographic Traveller (a great travel magazine) and PC Magazine for about 800 miles total.
As has been mentioned, all the ways of 'laundering' miles from one airline to another cost a hefty premium. I believe that in addition to HHonors, Amtrak's reward program is another potential laundry, but it too will severely discount your miles.
The best use of orphaned miles/points, IMHO, is to move them once (rather than twice for inter-airline transfer) into an affiliated program. Usually this means moving miles to hotel points, though occasionally it is sometimes worthwhile to move points to miles.
I do have a long term FF strategy for you. I assume that your prefer Marriott brands for hotel stays based on your points there. I am like you in that aspect, but I think you should consider Hilton as a secondary hotel chain. It is very easy to obtain and maintain Gold status within the HHonors program. Typically, one or two times a year, they will offer a promo where, if you have 4 stays (not nights) with them over a 90 period, they will give you 50K bonus points and elevate you to gold status for the next year or so. As the 4 stays can be at any Hilton property including Hampton Inns, this can be done very cheaply. Additionally, you can requalify your status using these promos. The only down side to this that everyone seems to be Gold with HHonors and one rarely gets upgrades (beyond executive floor rooms), but you should be used to this with Marriott.
Once you have reached gold status with HHonors, you become eligible for their
VIP Awards. The best ones are the GLON and GLONP awards at the bottom of the page. With these awards, for 100k-150k points, you can stay for six nights at some of their best hotels around the world. These include the Waldorf-Astoria in NYC, Palmer House in Chicago, Hilton Hawaiian Village, Hilton Waikoloa, Jalousie Hilton in St Lucia, Hilton Bankok, Hong Kong Conrad, Hilton Batang Ai Longhouse Resort in Malaysia, Hilton Sorrento Palace in Italy.... I am using a GLON award next spring for the Hilton in Auckland, NZ.
Note that you can change your MX and DL miles to HHonors on a 2-for-1 basis. In this case, the 2-for-1 is in your favor and would net you about 64k points with HHonors. Combine those with the 50k from the gold promo and you have enough points for a GLON award or be well on your way to a GLONP.
Although you probably have a Marriott or AA affinity credit card, continue to watch for other credit card deals. Last year DL launched a new Optima card program where many of us netted >50k miles in bonuses. Although I have not flown DL in years, I applied for the card. Recently I received my final 50k bonus from using it and quickly converted the miles to HHonors points to 'pay' for my GLON award in Auckland!
Again, let me welcome to FlyerTalk. Most of the biggest deals/promos do get mentioned in MilesBuzz!, but many only get talked about in their relevant sections of the message board. Look around and don't be afraid to ask questions, but do try to use search functions.
Have fun, but beware. This place is addicting!
[This message has been edited by BillMorrow (edited 10-20-2001).]